From Hard Drop - Tetris Wiki
The following are brief definitions of terms related to Tetris and similar games.
 Diagram Legend
The following is a legend detailing the functions of the various blocks used in the diagrams throughout the wiki articles.
|Empty playfield cell|
|Red block (commonly part of Z tetromino)|
|Orange block (commonly part of L tetromino)|
|Yellow block (commonly part of O tetromino)|
|Green block (commonly part of S tetromino)|
|Cyan block (commonly part of I tetromino)|
|Blue block (commonly part of J tetromino)|
|Purple block (commonly part of T tetromino)|
|Gray block (Garbage or Playfield wall)|
|Ghost piece or Line clear|
|Rotation center of a piece, a bomb in Bombliss, or any other specially marked block|
|Purple block for the T Tetromino when executing a T-Spin|
|Cell that has to be occupied for something (like a wallkick) to happen|
|Cell that cannot be occupied for something (like a wallkick) to happen|
- Gravity speed of 0 cells per frame where tetrominoes do not automatically drop when spawn. See G.
- Gravity speed of 20 cells per frame where tetrominoes instantly spawn on top of the stack. See G.
- Active piece
- Alternate term for falling piece.
- Alternate term for multiplayer garbage sent coined by Tetrinet players.
- All Clear
- When the player clears the whole playfield without leaving any blocks behind. Also known as a Bravo or Perfect Clear.
- A term for entry delay originating from Japan.
- Arika Rotation System (ARS)
- The rotation system used by most games published by Arika.
- Any combination of two or more line clears consisting of either a tetris or a T-Spin without any other line clear between them.
- A class of randomizer in which a collection of pieces is shuffled, and all are dealt into the preview. (See Random Generator.)
- Base (T-Spin)
- The portion of a T-Spin setup, not directly under an overhang, where the T rests upon.
- A solid element occupying one cell of the playfield. Also used as a synonym for "cell" to represent a length or width (e.g. a 2-block-tall hole). Multiple blocks make a piece such as a tetromino. In some publications, a "block" may refer to a whole piece, but Tetriswiki uses "piece" or "tetromino" for clarity.
- Bounding box
- A conceptual mechanism for explaining rotation systems that allows depicting how orientations are positioned relative to one another.
- When the player clears the whole playfield without leaving any blocks behind. Also known as a All Clear or Perfect Clear.
- Broken line
- Any line sent to opponents with only one gap in the row. In the typical multiplayer variant, broken lines are clearable and have at least one gap in a random location.
- Buffer Zone
- An invisible area above the matrix used to detect lock out, block out, and top out game over conditions. The dimensions of the buffer zone are the same as those of the matrix.
- The horizontal line separating the in-bounds rows of the playfield from the out-of-bounds rows. Most games place the ceiling at the top of row 20. In most games, the ceiling coincides with the top of the visible portion of the playfield.
- A unit square within the playfield.
- Channel (tetrising)
- The hole to place a vertical I tetromino for a tetris.
- The group of vertical cells inside the playfield, numbered from left to right.
- The act of clearing lines with consecutive tetrominoes, common to many recent Guideline games.
- The act of clearing lines in quick succession under a timer-based counter, as seen in Cultris.
- The act of clearing consecutive non-single line clears, as seen in the TGM series.
- Delayed Auto Shift. Refers to the delay prior to when the auto-repeat kicks starts.
- Refers to any or all of the following: entry delay, delayed auto shift (DAS), DAS delay, line clear delay, and lock delay.
- The act of clearing existing blocks inside the playfield to lower the height of the stack. Most commonly used in multiplayer Tetris to refer to clearing garbage sent by an opponent.
- Downward movement of a piece.
- Entry delay
- Time between when one piece finishes and when the following piece enters.
- Falling piece
- The tetromino or other piece under the player's control.
- Fast drop
- Another name for soft drop.
- Firm drop
- Manual downward motion of a tetromino where the piece lands within a frame and begins the lock delay.
- Floor kick
- Upward movement of a piece when it rotates against the floor of the playfield or other blocks.
- Period during which the sequence of rotation, movement, and gravity is executed, and the result is displayed. Video games in Japan and North America run at 60 frames per second.
- A tetris column with a 2-3 cell wide opening at the top for skimming.
- A unit of speed of one cell per frame. Refers most often to gravity; can also refer to DAS or soft drop speed. For example, when gravity is 20G, each piece falls so quickly that it instantly spawns on top of the playfield.
- Gap (tetrising)
- Same as Rectum.
- Rows of blocks added to the bottom of the playfield at the start of the game or during the game.
- Garbage blocking
- Garbage blocking is a feature that delays lines in the Receiving queue from appearing on the playfield until a piece is dropped which fails to clear a line.
- Garbage countering
- Sending garbage in order to reduce or eliminate lines in the Receiving queue.
- Ghost piece
- A marker in the playfield showing where the falling piece will land. Also known as Temporary Landing System (TLS).
- The automatic downward movement of a piece over time.
- The specification for how Tetris games made in roughly 2001 and later should operate.
- Hard drop
- Manual downward motion of a tetromino where the piece lands and locks instantly within a frame.
- Placing the falling piece in storage and moving the piece that was in storage (or next in line if no piece was in storage) to the top of the playfield.
- Hold Queue
- The storage place where players can Hold any falling Tetrimino for use later. When called for, the held Tetrimino swaps places with the currently falling Tetrimino, and begins falling again at the generation point.
- Hollow but enclosed cell(s) inside the stack.
- The open column to place a vertical I tetromino for a tetris.
- Initial Rotation System (IRS)
- A rule allowing the player to rotate a piece as it enters the playfield by pressing and holding a button during entry delay.
- A rule in which lock delay resets every time a piece is shifted or rotated.
- Jiznickery 
- A misdrop due to an inadvertent zangi-move. It happens in games with firm drop when the player drops a piece but does not wait long enough for the piece to lock before trying to charge DAS or input IRS for the next piece. The New Tetris was especially susceptible due to its lack of manual locking.
- A lagdrop is when a player drops a tetromino in the wrong place, or in the wrong orientation as a result of lag.
- Landing (tetromino)
- When the active tetromino makes contact with the surface of the stack or the bottom of the playfield.
- Line clear delay
- Common term to refer to a row in the playfield.
- Line clear
- Creation of a complete row of blocks with no holes after a piece locks. It disappears, and the blocks above the row move down.
- Line clear delay
- The time it takes for a Line clear to complete.
- After a piece has landed on the floor of the playfield or on other blocks, it becomes part of the playfield and is no longer subject to the player's control. Or to cancel lock delay, causing a piece to lock immediately.
- Lock delay
- The time between when a piece lands and when it locks.
- See Lock.
- Lock Out
- To top out by locking a piece above the ceiling. 
- Lines per minute (LPM)
- The average number of lines in the Tetris field that the player has cleared, per minute.
- A term used by The Tetris Company for a playfield.
- A term used by The Tetris Company for a block; this sense is little used outside TTC.
- The "block creatures" in the games Tetris Worlds and Kids Tetris are also called Minos.
- In Japanese Sega Tetris/TGM parlance, the term is used as an abbreviation of "Tetramino", thus referring to the whole piece instead of a single cell. The term "block", however, is used more often.
- Alternate term for misdrop.
- A misdrop is when a player accidentally drops a tetromino in the wrong place, or in the wrong orientation.
- Move reset
- Another name for Infinity.
- Next piece
- Alternate term for piece preview.
- Notch (T-Spin)
- The crevice in a T-Spin setup that is directly under an overhang.
- Open column
- The hole to place a vertical I tetromino for a tetris.
- The direction that a piece faces. The number of orientations in Tetris pieces may not always be equal to the number of geometric orientations a shape can take. Shapes like Z, S, and I which only has two orientations, or O, which has only one, can be treated as having four internal representations in some games, most commonly those that implement the Super Rotation System.
- A block or column of blocks extending from a wall of blocks over an empty cell or column. Overhangs are commonly used as a method of reordering piece placements when a player recieves undesirable tetromino sequences. In games where T-Spins are rewarded, overhangs may be used to set up a T-Spin.
- A set of blocks that moves as a unit.
- Piece preview
- A display area of the tetrion devoted to displaying the next pieces that will enter the playfield.
- Perfect Clear
- When the player clears the whole playfield without leaving any blocks behind. Also known as a All Clear or Bravo.
- A grid of cells into which pieces are placed.
- Random Generator
- A specific randomizer used in newer games that guarantees an even distribution of piece types. It consists of a bag with one of each of the seven tetrominoes.
- An algorithm that generates a sequence of piece types.
- Receiving Queue
- A vertical meter that accrues opponents’ line attacks between lock downs. When a lock down occurs, any lines accrued in the meter are added to the bottom of that player’s matrix before generation of the next tetrimino.
- The open column to place a vertical I tetromino for a Tetris. It consists of at least four adjacent rows that are filled with blocks except for a single hole in the same column. The term comes from the Latin for "straight".
- To change a piece's orientation by turning it clockwise or counterclockwise, generally by 90 degrees.
- Rotation system
- A rule specifying the orientation for each piece type and the movements (including wall kicks and floor kicks) when changing orientations.
- The group of horizontal cells inside the playfield, numbered from bottom to top.
- Alternate term for ghost piece.
- Soft drop speed
- Moving a piece sideways.
- Line clearing the edge or surface of a stack to purposely downstack, flatten the field, or upstack for a tetris.
- The horizontal line at the top of the matrix. Tetriminos fall from the middle of the matrix just above the skyline.
- Placing a piece under an overhang by moving it sideways.
- Solid Line
- A row of blocks without any gaps sent to one or more opposing players.
- Sonic drop
- A name for firm drop arising from the TGM community.
- Spawn location
- Where the active tetromino enters the playfield.
- The rate at which the active tetromino automatically falls. See Gravity.
- The rate at which a player drops a tetromino. See Tetromino Per Time.
- The specific delay values that determine how fast a game can be played optimally, or how slow it can be played for survival.
- Super Rotation System (SRS)
- A rotation system for tetrominoes used by games that adhere to the Tetris Guideline.
- The structure created from placing tetrominoes inside the playfield.
- The act of placing tetrominoes inside the playfield.
- Starting line
- Any broken or solid line at the beginning of a game. Typically, variants may use different preset or random patterns to mix up game play.
- Step reset
- Lock delay resets every time the falling piece moves downward.
- Target Mark
- A movable marker that designates the recipient of a line attack. This marker displays near the middle of the opponent’s matrix but is only visible to the player that controls it.
- Tool-assisted speedrun. A performance produced by means unavailable to regular players, such as slow motion, frame-by-frame advance of the gameplay, or re-recording of previous portions of a performance.
- Effect of failure to adapt to different variations of a puzzle game, especially different rotation systems. (Coined by colour_thief as a portmanteau of "tetromino" and "jet lag".)
- Alternate term for tetromino used in Nintendo Power reviews of 8-bit Tetris games and in the initial release of the video game StarTropics 2.
- Alternate term for tetromino allegedly used by The Tetris Company in the late 1990s.
- Alternate term for tetromino used by The Tetris Company as of Tetris Worlds.
- A term used by The Tetris Company for the game object that contains a playfield. Different tetrions may implement different variations of the game rules. (Not to be confused with treknobabble.)
- The Tetris Company's trademark for products implementing the Soviet Mind Game.
- The act of clearing four lines with one tetromino.
- Top out
- A piece reaches the top of the playfield and the game ends.
- Any block formation such that when the T-Tetrimino is spun into it, any three of the four cells diagonally adjacent to the center of the T-Tetrimino are occupied by existing blocks.
- A twist performed with the T tetromino that satisfies specific requirements.
- T-Spin Single
- A T-Spin that clears one line.
- T-Spin Double
- A T-Spin that clears two lines.
- T-Spin Triple
- A T-Spin that clears three lines.
- Placing a piece under an overhang by rotating it.
- The act of placing tetrominoes inside the playfield to increase the height of the stack.
- Wall kick
- Sideways movement of a piece when it rotates against the floor of the playfield or other blocks.
- A term used in some older games for the playfield.
- Getting Xealed; Xealing; Xealed it;
- A term used for sending more lines than your opponent and losing.
- Double Xealed means sending more lines than two opponents and losing, Triple, Quad, etc.
- All Xealed means sending more than everyone put together and losing.
- Counter Xealed is when you Xeal a player and that player responds by Xealing you back. This image demonstrates a Counter Xeal. 
- Named after player Xeal, who tends to do it a lot.
- Moving a piece downward, sliding it, and locking it.
 See also
- Term Correspondence Chart for Japanese terms
- TGM legend for more explanation of terms used with the TGM series