the female equivalent of a cock block, to "plug a rug" is to impede a female during flirtation or other attempts at mating with the opposite sex. the phrase is a combination of the word rug, here reffering to the pubic hair of a womans vagina, and the word plug, or to block off a hole, such as the vagina, thus creating the phrase "plug my rug" or "block off my vagina" or "prevent me from getting dick tonight", which are all synonymous with each other.
"oh my gosh tiffany, i was totally talking to charlie before you came over here and interrupted us! way to plug my rug, bitch!"
"jesus christ, that cute guy over there is walking towards me, kelsey! dont plug my rug, ok?"