Adulterer (or adulteress) can be used for anyone who has a sexual relationship with a person who is married to another, but again does not always imply the specific social situational that mistress does.

What is it called when you sleep with a married man?

Photo: Zohar Lazar. There is a certain kind of woman who tends to sleep with married men. Sometimes called a backdoor girl, she is usually self-sufficient and lives alone, two qualities that make her appealing to husbands looking for some action on the side.