A bung-hit is when person
A (receiver) seals their lips
around persons B's (giver) anus. Then person
A passes gas and person
B inhales deeply and holds their breath.
Offering, or suggesting, that someone receive a bung-hit is considered to be a vulgar insult
to many; and therein
lies its value in communication.
In a sarcastic and obnoxious tone:
"Hey, why don't you plant your lips
around my anus and I will fart
and you inhale
deeply. Have you ever had a bung-hit before?"