paramour

Etymology

From Middle English paramour, paramoure, peramour, paramur, from Old French par amor (“for love's sake”). The modern pronunciation is apparently an Early Modern English readaptation of the French.

noun

1. (somewhat archaic) An illicit lover, either male or female.
   to run away with a paramour
   The seducer appeared with dauntless front, accompanied by his paramour. 1848, Thomas Maucalay, The History of England from the Accession of James the Second
   They should be chaste, not lustful, nor taking paramours: 1934, Yusuf Ali, transl., The Holy Qur'an: Text, Translation and Commentary, surah 4, verse 25
   The action scenes are deafening and punchily staged by director Louis Letterier (The Transporter), though I wish he’d set more time aside to spend with Nobby, his paramour Dawn (Rebel Wilson), their shaven-headed brood, and friends 23 February 2016, Robbie Collin, “Grimsby review: ' Sacha Baron Cohen's vital, venomous action movie'”, in The Daily Telegraph (London)
2. (obsolete) The Virgin Mary or Jesus Christ (when addressed by a person of the opposite sex).

verb

1. To go with a paramour; to have an affair.
   The paramouring matron left / A babe and husband both bereft; 1842, John de Jean Fraser, The Stranger in His Native Place
   This meant it could even call in "third party 'paramours'" and tell them to quit their paramouring. 2011, Joanna L. Grossman, Lawrence M. Friedman, Inside the Castle, Princeton University Press

adv

1. (obsolete, of loving, etc.) Passionately, out of sexual desire.