paramour

noun

1. an illicit lover, especially of a married person.
2. any lover.

noun

1. mainly derogatory a lover, esp an adulterous woman
2. an archaic word for beloved (def. 2)

n.c.1300, noun use of adverbial phrase par amour (c.1300) “passionately, with strong love or desire,” from Anglo-French and Old French par amour, from accusative of amor “love,” from amare “to love” (see Amy). Originally a term for Christ (by women) or the Virgin Mary (by men), it came to mean “darling, sweetheart” (mid-14c.) and “mistress, concubine, clandestine lover” (late 14c.).