Polacca \Po*lac"ca\, n. [It. polacca, polaccra, polacra; cf. F. polaque, polacre, Sp. polacre,] [Written also {polacre}.] 1. (Naut.) A vessel with two or three masts, used in the Mediterranean. The masts are usually of one piece, and without tops, caps, or crosstrees. 2. (Mus.) See {Polonaise}.