The Collaborative International Dictionary of English v.0.48:

Dabbler \Dab"bler\ (d[a^]b"bl[~e]r), n.
   1. One who dabbles.
      [1913 Webster]

   2. One who dips slightly into anything; a superficial
      meddler. "our dabblers in politics." --Swift.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dabbler
    n 1: an amateur who engages in an activity without serious
         intentions and who pretends to have knowledge [syn:
         dabbler, dilettante, sciolist]
    2: any of numerous shallow-water ducks that feed by upending and
       dabbling [syn: dabbling duck, dabbler] [ant: diving
       duck]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "dabbler":
   Sunday painter, abecedarian, amateur, coquet, criticaster, dabster,
   dallier, dilettante, dunce, flirt, fool, fribble, grammaticaster,
   greenhorn, greeny, half scholar, ignoramus, illiterate, illiterati,
   know-nothing, lowbrow, middlebrow, no scholar, nonprofessional,
   philologaster, philosophaster, piddler, potterer, puddinghead,
   putterer, sciolist, smatterer, tenderfoot, trifler, tyro,
   unintelligentsia