An illicit or clandestine lover or mistress, esp. taking the place of a husband or wife; (now Scots Law and U.S. Law) the person with whom a…

In reference to illicit relations: a paramour or lover (applied to both men and women). Obsolete.

A male or female lover. Also (frequently derogatory): a man or woman kept for sexual favours; a mistress or paramour. Obsolete.

One who carries on an intrigue or liaison.

An extramarital affair; sexual relations with someone other than one’s spouse or partner. Also: the person with whom one conducts such an affair…