The Collaborative International Dictionary of English v.0.48:
kept \kept\ (k[e^]pt), imp. & p. p. of Keep. [1913 Webster] Kept woman, Kept mistress, a concubine; a woman supported by a man as his paramour. [1913 Webster]WordNet (r) 3.0 (2006):
kept woman n 1: an adulterous woman; a woman who has an ongoing extramarital sexual relationship with a man [syn: mistress, kept woman, fancy woman]