One who displays loser-like qualities; one who sucks at pretty much anything; one who pets kittens.
Patricles: Dude, you just got killed 5 straight times in Halo,you are such a kittenpetter.
Michelle: You know what, you're a black kitten petter!
Crowd: oooooo, that's the worst kind.
Kittenpetter easily takes the place of the word "noob."