When you accidentally give oral sex to someone with poor genital hygiene.
Luke: Shit man, you don't look so good!
Cornelius: I just had a green onion cake...
A girl who pretends to have her period so that she doesn't have to have sex.
Doug: Jenn is so hot!
Ian: Don't waste your time, she's just a can of ketchup.
a person (normally female) with poor genital hygiene.
Chelsea forgot to wash her vag for 6 days, and she turned into a green onion.