A female's Vagina.
More correctly, a female's Vagina that has had a penis within it's domain.
Often referred to a female's vagina that enjoys many penises, or has had many penises within (inside) it's territory.
Matt: Whoaaa! Jeremy, who's that attractive young chick over there?
Jeremy: No way dude! Stay away from that one. She's a total meat vacuum. She'll take any rod in her she can get. Baaaaad news.