French Hairline

A hairline that is retreating to the back the head.

John: Oh my?!? Jim, what happened to your hair??
Jim: I got a bad haircut
John: No, you got yourself a french hairline, you gotta embrace it and shave the lot or start wearing a hat.
Jim: what’s a french hairline?
John: It’s retreating...to the back of your head.
Jim: huh
John: you’re going bald. Soon there will be no clear definition of where your forehead ends and your scalp begins.