Generally used as a more powerful, masculine alternative to the typically "soft" and feminine nicknames such as pussy, coochie, etc. Can also refer to a gay man's anus, where it would substitute for words such as fox hole or mangina.
Female (lifting box): "Suck my vatro, prick!"
2) "Yo girl, you got a tampon up in this bitch? My fucking vatro just started bleeding like a mofo."
3) Gay male to boyfriend: "...That's not what you said last night when your tongue was all up in my vatro, bitch!"