A girl that you only call or booty call on Tuesday nights, to chill with or fuck, when nothing else is going on. Opposite of a Friday night girl. Usually more clingy and less attractive than a Friday night girl, but she puts out and mostly keeps quiet about it.
A girl you don't introduce to your parents or your friends. She serves her purpose, sexually, maintenance fee's are real low. But she does not get top date night billing like Friday or Saturday night. She may move up higher in the rotation if she can cook bonus if she does your laundry
My Monday night girl is coming over to make me a meatloaf and blow me watching football. Hope I beat the point spread on the shop football pool