Lewis & Short

dicrŏtum, i, n. (sc. navigium), = δίκροτος (two-oared), a galley with two banks of oars, Cic. Att. 5, 11, 4; 16, 4 fin.
Also called dicrŏta, ae, f. (sc. navis), Auct. B. Alex. 47, 2.