The Collaborative International Dictionary of English v.0.48:

Enthusiastic \En*thu`si*as"tic\, Enthusiastical
\En*thu`si*as"tic*al\, a. [Gr. ? .]
   Filled with enthusiasm; characterized by enthusiasm; zealous;
   as, an enthusiastic lover of art. "Enthusiastical raptures."
   --Calamy. -- En*thu`si*as"tic*al*ly, adv.
   [1913 Webster]

         A young man . . . of a visionary and enthusiastic
         character.                               --W. Irving.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Enthusiastic \En*thu`si*as"tic\, n.
   An enthusiast; a zealot. [Obs.] Enthymematic

WordNet (r) 3.0 (2006):

enthusiastic
    adj 1: having or showing great excitement and interest;
           "enthusiastic crowds filled the streets"; "an
           enthusiastic response"; "was enthusiastic about taking
           ballet lessons" [ant: unenthusiastic]

Moby Thesaurus II by Grady Ward, 1.0:

150 Moby Thesaurus words for "enthusiastic":
   ablaze, acquiescent, active, acute, afire, aggressive, agreeable,
   alacritous, amenable, animated, ardent, attracted, avid,
   boiling over, breathless, brisk, buggy, bugs, burning, cathectic,
   compliant, concerned, consenting, content, cooperative, cordial,
   curious, delirious, devoted, disposed, docile, drunk, dynamic,
   eager, earnest, emphatic, energetic, enterprising, enthused,
   enthusiastic about, excited, exciting, exuberant, fain, fanatical,
   fascinated, favorable, favorably disposed, favorably inclined,
   febrile, fervent, fervid, fevered, feverish, fiery, flaming,
   flushed, forceful, forcible, forward, full of enthusiasm,
   full of pep, gaga, game, glowing, go-go, gone on, gung ho, gung-ho,
   hearty, heated, hipped, hopped-up, hot, impassioned, impetuous,
   in the mind, in the mood, incisive, inclined, infatuated with,
   intense, interested, intoxicated, irrepressible, keen, keen on,
   kinetic, lively, living, lusty, mettlesome, minded, nutty,
   obsessed, on fire, passionate, peppy, piqued, pliant, predisposed,
   prompt, prone, provoking, quick, rabid, ready, ready and willing,
   receptive, red-hot, responsive, robust, smacking, snappy, spanking,
   spirited, steaming, steamy, stimulating, stirring, strenuous,
   strong, take-charge, take-over, tantalized, tickled, titillated,
   tractable, trenchant, turned-on, unqualified, unrestrained,
   unstinting, urgent, vascular, vehement, vibrant, vigorous,
   vivacious, vivid, warm, well-disposed, well-inclined, willed,
   willing, willinghearted, zealous, zestful, zesty, zippy