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.
To top out when a block overlaps the entry position. 
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 All Clear.
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.
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 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.
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.
Creation of a complete row of blocks with no holes after a piece locks. It disappears, and the blocks above the row move down.
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.
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.