The Collaborative International Dictionary of English v.0.48:
litterbug \lit"ter*bug`\ (l[i^]t"t[~e]r*b[u^]g), n. a person who litters public places with refuse. Syn: litterer, litter lout. [WordNet 1.5]WordNet (r) 3.0 (2006):
litterbug n 1: a person who litters public places with refuse [syn: litterer, litterbug, litter lout]