concŭbīnātus

I. Union of a man with an unmarried woman (usu. of a lower social grade than himself), concubinage (opp. matrimonium on the one hand, and adulterium or stuprum on the other; not in Cic.): emere aliquam in concubinatum sibi, Plaut. Poen. prol. 102: in concubinatum alicui dare (opp. in matrimonium), id. Trin. 3, 2, 64; cf. Dig. 25, 7, 1; 48, 5, 13.—*

II. Adulterous intercourse: nuptarum, Suet. Ner. 28.