noun
adulteress; unfaithful woman
A woman who cheats on her partner; carries a strong negative moral judgment. Less common in modern speech than 浮気する女 or 不倫相手, but still understood.
彼は妻が浮気女だと知ってショックを受けた。
He was shocked to learn that his wife was an adulteress.
Compound of 浮気 (うわき, 'unfaithfulness') and 女 (おんな, 'woman'). The exact historical derivation is uncertain, but the meaning is transparent from its components.