Noun
other woman (plural other women)
(informal) A woman who is romantically involved with someone (usually a man) already in a committed relationship with another woman, especially a woman having an affair with a married man.
Coordinate term: other man
Hypernym: home wrecker
Remembering the turmoil she experienced when her father left her mother, she vowed she would never be the other woman.
Don't tell a woman she's pretty; tell her there's no other woman like her, and all roads will open to you. Jules Renard
I met a girl who works at the Double Tree front desk, she gave me her phone number. It's zero. I tried to call her from here and some other woman answered. I said "You sound older!" Mitch Hedberg
I do regard her as one who is too modest for the world in general to be aware of half her accomplishments, and too highly accomplished for modesty to be natural of any other woman. Jane Austen
I would rather have your friendship than the love of any other woman in the world! Anne Brontë
I never cease to wonder at my luck in having for my sister the woman who, more than any other woman in America, possesses all the qualities of true greatness. Lillian Gish
A truly happy woman drives some men and almost every other woman absolutely crazy. John Irving