Lancer \Lan"cer\, n. [Cf. F. lancier.] 1. One who lances; one who carries a lance; especially, a member of a mounted body of men armed with lances, attached to the cavalry service of some nations. --Wilhelm. 2. A lancet. [Obs.] 3. pl. (Dancing) A set of quadrilles of a certain arrangement. [Written also {lanciers}.]