Lots of funk musicians use the word nasty when they mean seriously groovy, you dig?
There seems to be a usage in modern culture where nasty means something slutty, sexy, pornographic, or something along those lines. "Nasty girls".
Can it be slang for vagina, as opposed to the act of sexual intercourse? See dry as a nun's nasty. Equinox ◑ 23:41, 13 February 2015 (UTC)