A fork of Rural Dictionary
An individual who commits oral on a girl at the beach, thus leaving sand in his/her mouth. The end result: a sandy surprise.
Wow! That kid Jack is a real sand muncher!
to put inside or pull inside, i.e. have sex or get barreled (tubed) surfing... i.e. the most pleasurable things you can do. term can be adapted to other situations requiring guts/skill
check out that chick, I like puinsai...
or
did you see Rodney's wave, he puinsai...