Is there a word for a male "mistress"?

Search: mistress male

Why: Is there? Like the man with whom a married woman has an affair?

Answer: No! The definition of mistress is:

• woman having sexual relations on a regular basis and being supported by man not her husband

and the closest equivalent is gigolo - which doesn't mean "male prostitute," but:

1. a man living on the earnings of or supported by a woman;
2. a professional dancing partner or male escort

Some findings:

• 220 English words meaning “promiscuous woman,” but only 20 for “promiscuous man”
• 500 slang terms for “prostitute”
• 65 slang terms for “whoremonger” and “pimp,” meaning men who sell women for sexual purposes
• A male tramp lacks a regular job and place of residence. A female tramp is a whore.
• Originally, master and mistress were equivalent words for persons having control or authority over others. Mistress in the sense of “a woman who employs others or has authority over servants” is from 1426. By 1430 the word had taken on the sense of “kept woman of a married man.”

Source: Daily Writing Tips

The More You Know: Katrina said something about a "mastress" or something on "How I Met Your Mother." Sounds like another reason I don't watch that show.