A situation when a piece or a pawn cannot or is forbidden to move because it could expose the king for an attack or would expose a more valuable piece behind it to capture.
In the following example Qa3 and Re7 are pinned.
ECHESSPEDIA
Quotes of the Day
When you see a good move, look for a better one
Emanuel Lasker
The main thing is that you’ve got to keep on studying however old you are. You can’t just rely on your capital, so you have to try and keep up, and that is a difficult task.
Nigel Short 2016
Chess is respected in culture and education, but our organization is far behind. FIDE must lead, not drag chess down.
Garry Kasparov 2014
You only task in the opening is to reach a playable middle game.
Lajos Portisch
There is no room for gallantry in chess.
Irving Chernev