Acronym for Happy Blow Job Face. That absurd smile where you open your mouth really wide and smile like that. Usually when you're really excited. Or mocking something. The "h" for happy can be replaced with pretty much any other emotion. you can have a cbjf (confused blow job face) or an abjf (angry blow job face)or a fbjf (frightened blow job face)....you get the idea. All are executed by opening the mouth wide and then making the matching facial expression. Like looking angry with your mouth open wide. You get it.
"She had a total hbjf when I told her I was going to fuck her tonight."
"She had a total abjf when I told her I fucked her boyfriend last night"
"OMGOMGOMGOMGOMGOMG THIS IS SOOOOOO EXCITING *makes hbjf*"