chin rub 

when you think someone or something is stupid, you chin rub.
normally you look at them like they are stupid and rub your chin hinting that what they just said is dumb. but when you cannot see the person or do not feel like rubbing ur chin like you have a beard you say chin rub so people know thay wat they said was amazingly stupid and idiotic.

Sean: theres nothing to do
Mike: i knoww man....lets go to the park or something.
Cindy: wow mike, chin rub its raining u dumbshit.

chin rub by melliissaaaa May 20, 2008

chin-rubbing 

when ones nuts are hot and sweaty from sex, and someone is giving that person head and there nuts are hitting the other person's chin.

when Randy, Josh, & Matt have oral sex, they all have a good ol chin-rubbing.

chin-rubbing by christinamber May 9, 2008