Term to describe when a girl has a noticeable amount of facial hair. It comes from when a person has mustard, ketchup etc. on their face from eating food, and also french girls, since they sometimes do not shave.
So French Mustard is a combination of the two.
Friend 1: Hey how did that blind date go??
Friend 2: Oh, well, she had a nice body and all, shes actually nice, but i noticed some French Mustard.
Friend 1: Ohhh, thats a boner killer. well, she can always shave it off.
Friend 2:True she could shave, but how do i tell her to without being an ass?
Friend 1: I guess you cant, you will just have to deal with the French Mustard.