The act of performing oral sex on a stinky or otherwise unclean vagina. The phrase gets its name from the rather oniony smell that used and unclean vaginas carry.
Bro 1: Man, I had an onion sandwich today.

Bro 2: Yeah I can smell you from here. Tell Monica to wash her snatch.
by Mega Hemroids August 16, 2019
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where you masturbate in the high school bathroom, while sitting on a broomstick. At the same time, a short stocky friend with huge calves masturbates into your mouth. the vice principal walks in and you cum and shit onto a pregnancy test. later on you do sexual things with cookie.
why isn't josh in school today? he was too busy making an onion sandwich.
by Rhyda Broomstik September 23, 2009
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