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U

Udemann Code: Chess notation created to be transmitted via telegraph.

Ufimtsev Defense: 1 .e4 g6 2. d4 Bg7.

Under promotion: Promoting a Pawn which has reached the eighth rank to a piece other than a Queen.

Undoubling: To move one of a set of doubled Pawns onto an adjacent file which contains no Pawns of its own color, via a capture.

Unit: A term which refers to both pieces and Pawns.

USCF: United States Chess Federation. Official governing body for Chess in the United States. Often referred to by its abbreviation, USCF.