barf means: To vomit, indulge in reverse peristalis. Ok, it means throwing up. It's used for the action of throwing up or the stuff that you throw up (like puke). "I think I'm gonna barf." "Well don't get barf on the floor, my parents will get mad!". This was a pretty common word when I was in elementary school. It was used from kindergarten up to about fourth or fifth grade.