This is a lie a married man tells to a woman he is not married to in order to get her to have sex with him.
Lou was hitting on his hairdresser and she asked him "Lou, aren't you married?" Lou answered, "No, I am divorced, have been for 11 years." (Lou has actually been married for over 20 years).
Lou continues to hit on his hairdresser until she finally gives in to his advances. Because of Lou's little wife lie, the hairdresser has unknowingly become "the other woman"