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.
One's facial expression when they have a boner.
It is more to do with the horny aura than with an actual boner. There is a slight smile, glint in the eyes and laid back body with the dick as the controller of all thoughts.