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
We lost the crowns of World Champions, it is sad, of course. But if you look at the rating list of top 100 players, Russia is still dominating. However, the competition is constantly growing stronger.
Arkady Dvorkovich 2011
Chess is a fairy tale of 1001 blunders.
Savielly Tartakower
I don’t believe that Garry likes making decisions by democratic procedures. When there is a decision that he doesn’t like, he just turns against this organization.
Georgios Makropoulos 2013
” Chess is most certainly not my life.”
Tony Miles
Preparation for a world championship was always an arms race, in previous times with books, then with seconds, today with computers.
Vishy Anand 2008