An insult one gives to another be it male or female. Males tend to get more offended because it implies that they A) have a vagina therefore they must be a girl...or a hermaphrodite and B) Their vagina stinks like garlic.. twice offended with one insult. Females would be offended because it implies that they don't wash often and therefore their vagina stinks like garlic. Whoever you say it to, it's bound to get an unpleasant reaction somewhere down the line. The term can also be used in conjunction with 'Your mother' insult for added effect.
Guy1: Yo dude, stfu go lick your ma's garlic vag. Guy2: wtf, nigga stfu you're the one with the garlic vag! Guy1: Fuck you and your garlic vag! | Guy2Girl: Hey do you smell that?? It smells like garlic vag.. ewww it's you isn't it!!! DIRTY BITCH!! gtfo go and wash!! Girl2Guy: Umm, wtf are you on about. I don't have a 'Garlic Vag'. How could you even suggest such a thing. *closes legs and prenteds to sniff around her crotch to make sure it's not her*