1. A case of classic cheesin
in which you cannot wipe the smile from your face. A face boner is usually due to happiness in a relationship but it may be used in other instances as well.
*It is possible to experience a face boner and a real boner simultaneously.
Dude: I totally nailed a smokin' hot babe last night!
Chad: Dude you don't have to tell me, your face boner gave it away!