Halfpipe Head

When your head is so concave that it looks like a halfpipe.

"I heard Tamika is gonna be here tonight. You know, the chick with the dented head."
"Shit is beyond dented. She's got a straight halfpipe head. I'm gonna hit a 540 Indy Nosebone off that bitch if you know what I mean."
"No."

"Brendan is dumb as fuck. Man better not come at me with that halfpipe head."
"I heard his head collects water when it rains."
"Nuh uh, really?"
"No not really you idiot."
"Aw man. I have all this salsa with no bowl. You had me excited."