A dirty piranha is a piece of sh*t shaped like a cock, and shoved up a girls vag. its then pissed on. then the girl will take it, and give it a blow job.
"YO NOAH, yesterday i took a shit and soved it up jasmines vag! and she pissed on it! then gave it a blow job!"
"ian, me and sydney did the same thing, its called a dirty piranha!"