Lewis & Short

concŭbīnus, i, m., and concŭbīna, ae, f. [concubo], one who lives in concubinage (cf. concubinatus), a concubine (male or female), a less reproachful designation than paelex (cf. Dig. 5, 16, 144).

      1. a. Masc. (not in Cic.), Cat. 61, 130 sq.; * Quint. 1, 2, 8; Plin. 8, 45, 70, § 180; Curt. 10, 2, 27; Suet. Galb. 22; Tac. A. 13, 21; Mart. 6, 22.
        Far more freq.,
      2. b. Fem., Plaut. Ep. 3, 4, 30; id. Mil. 2, 1, 62; 2, 3, 66 al.; 2, 5, 6; 2, 6, 68; id. Merc. 4, 4, 17; id. Stich. 4, 1, 56; * Cic. de Or. 1, 40, 183; Tac. H. 1, 72 et saep.; cf. Dig. 25, 7: de concubinis.