The Collaborative International Dictionary of English v.0.48:

Humorous \Hu"mor*ous\, a. [Cf. L. humorosus, umorosus, moist.
   See Humor.]
   1. Moist; humid; watery. [Obs.]
      [1913 Webster]

            All founts wells, all deeps humorous. --Chapman.
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   2. Subject to be governed by humor or caprice; irregular;
      capricious; whimsical. --Hawthorne.
      [1913 Webster]

            Rough as a storm and humorous as the wind. --Dryden.
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   3. Full of humor; jocular; exciting laughter; playful; as, a
      humorous story or author; a humorous aspect.

   Syn: Jocose; facetious; witty; pleasant; merry.
        [1913 Webster]

WordNet (r) 3.0 (2006):

humorous
    adj 1: full of or characterized by humor; "humorous stories";
           "humorous cartoons"; "in a humorous vein" [syn:
           humorous, humourous] [ant: humorless, humourless,
           unhumorous]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "humorous":
   Attic, absurd, amusing, beguiling, biting, bizarre, brilliant,
   clever, comical, delightful, diverting, droll, eccentric,
   entertaining, facetious, farcical, fun, funny, hilarious,
   humorsome, hysterical, incongruous, jesting, jocose, jocular,
   joking, joky, joshing, keen, keen-witted, laughable, ludicrous,
   merry, mordant, nimble-witted, playful, pleasant, pointed,
   priceless, pungent, quaint, quick-witted, quizzical, rapier-like,
   recreational, rich, ridiculous, risible, salt, salty,
   scintillating, screaming, sharp, smart, sparkling, sprightly,
   titillating, titillative, waggish, whimsical, witty