This term has two different significations; sometimes it means a species of marriage which took place among the ancients, and which is yet in use in some countries. In this country it means the act or practice of cohabiting as man and woman, in sexual commerce, without the authority of law, or a legal marriage.
Law Dictionary – Alternative Legal Definition
A species of loose or informal marriage which took place among the ancients, and which is yet in use in some countries. See CONCUBINATUS. The act or practice of cohabiting, in sexual commerce, without the authority of law or a legal marriage. An exception against a woman suing for dower, on the ground that she was the concubine, and not the wife, of the man of whose land she seeks to be endowed. Britt c. 107.