When a woman is dating a married men they call her mistress, what do they call a man who dates married women?

A two timing louse.

You already have one thread with the very same question. Please keep your questions about the same subject on one thread..

Maistre

A two timing louse.

Applies to both of them in my book.

Deleted your other post since this one seems the most active

A target around here.

Glen