Hang brain is not the act of placing your scrotum on someone or something as noted in the other definitions. That would be "tea baggin." Hang brain is just the act of hanging your scrotum (testicles and all) out of the zipper of your pants.
The doctor wanted to see check my scrotum for unusual lacerations, so he asked me to hang brain.
04 Fevral 2004
special type of taunt, used to punctuate a command: say your command, then clap once, clap again, then put your arms up over your head, keeping elbows about a foot apart.
example: woman says "get me a drink" to man nearby, then clap-clap-arms up. The boy, either does it, or responds with a denial, and similar clap-clap-arms up.
21 Yanvar 2005