Glossary of Chess - U

U

Undermining

This is a chess tactic (also known as removal of the guard) in which a defensive piece is captured, leaving one of the opponent's pieces undefended or underdefended.

Underpromotion

Promoting a pawn to a rook, bishop, or knight instead of a queen. Rarely seen unless the knight can deliver a crucial check, or when promotion to a rook or a bishop instead of a queen is necessary to avoid stalemate.

Unpinning

the act of breaking a pin. This allows the piece that was formerly pinned to move.

United States Chess Federation (USCF)

This is a non-profit organization, the governing chess organization within the United States, and one of the federations of the FIDE.

Unorthodox opening

See Irregular opening.