Makes you look goofy, which is hard to do since you already have a helmet on your head and you're forty-seven.
"What now, Stan?"
"Bob... fucking unbuckle your chinstrap."
"Then what's the point of the helmet, Stan, huh, what then?"
"Then you fucking take the helmet off! You're an embarassment to men. Look, look at that five-year old over there. She's got a helmet on. Your forty-seven, Bob. Wait, just watch this... hey little girl?"
"What you old hags?"
"What do you think of this guy..." *thumbs over*
"The douchebag with that helmet?"
"Hey, I'm not a douchebag you little punk! And you have a helmet on too!"
"Um, yeah, because my mom tells me to; and it's also where I store my weed. Want some?"
"Fuck yeah, how much for a dime?"
A hard and heavy blow the chin as a form of minor punishment in prison/jail. Usually given for minor incursions. A head will tell a torpedo to administer the chinstrap.