One who gives oral sex to women,who usually is a lesbian. The 'rug' refers to the clit/pussy/vaggy/fuckholeetc... or perhaps the pubic hair of that region.
Also, in mens opinions, the 2nd best thing that has ever happened to the world, behind bisexuals.
Woman1: Munch me ruggy! Munch me!
Woman2: makes slurping noises