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