This is kind of swearword, and also kind of slangy anatomic term. I recommend not to use it anyway, this is very strong word( like three-letter word and others). If you still intrested in this term you can read some info here: (its just an article, fortunatly no illustrations are provided :) but if your not 18 i recommend not to read it, it containts strong language) http://ru.wiktionary.org/wiki/%D0%B7%D0%B0%D0%BB%D1%83%D0%BF%D0%B0