Quiescence search is an algorithm typically used to evaluate minimax game trees in game-playing computer programs. It is a remedy for the horizon problem faced by AI engines for various games like chess and Go.
 The horizon effect
Main article: horizon effect ...
The idea of quiescence is that the static evaluator should not be applied to positions whose values are unstable, such as those occurring in the middle of the piece trade.
The purpose of the quiescence search is to prevent horizon effects, where a bad move hides an even worse threat because the threat is pushed beyond the search horizon. This is done by making sure that evaluations are done at stable positions, i.e.
See also: What is the meaning of Artificial intelligence, Algorithm, Values, AI, Search algorithm?