The Collaborative International Dictionary of English v.0.48:

Amateur \Am`a*teur"\, n. [F., fr. L. amator lover, fr. amare to
   love.]
   A person attached to a particular pursuit, study, or science
   as to music or painting; esp. one who cultivates any study or
   art, from taste or attachment, without pursuing it
   professionally.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

104 Moby Thesaurus words for "amateur":
   Sunday painter, abecedarian, admirer, aesthete, aficionado,
   amateurish, apprentice, arbiter, arbiter elegantiarum,
   arbiter of taste, authority, avocational, beginner, bon vivant,
   booster, buff, bungler, bungling, clumsy, cognoscente, collector,
   connaisseur, connoisseur, coquet, crank, critic, criticaster,
   crude, dabbler, dabbling, dabster, dallier, devotee, dilettante,
   dilettantish, enthusiast, epicure, epicurean, expert, faddist, fan,
   fancier, flirt, follower, freak, fribble, good judge, gourmand,
   gourmet, grammaticaster, greenhorn, groupie, half scholar,
   half-assed, half-baked, half-cocked, idolater, idolizer, immature,
   inexpert, infatuate, inferior, judge, lay, layman, maven, mediocre,
   neophyte, nonprofessional, novice, nut, philologaster,
   philosophaster, piddler, potterer, probationer, pundit, putterer,
   refined palate, rooter, savant, scholar, sciolist, sciolistic,
   second-rate, shallow, smatterer, smattering, sophomoric,
   specialist, superficial, technical expert, technician, tinker,
   trifler, tyro, unpaid, unprofessional, unskilled, untrained,
   virtuoso, votary, worshiper, zealot