1. 
[syn: amusing, comic, comical, funny, laughable, mirthful, risible]
The Collaborative International Dictionary of English v.0.48:
Risible \Ris"i*ble\, a. [F., fr. L. risibilis, fr. ridere,
   risum, to laugh. Cf. Ridiculous.]
   1. Having the faculty or power of laughing; disposed to
      laugh.
      [1913 Webster]
            Laughing is our busines, . . . it has been made the
            definition of man that he is risible. --Dr. H. More.
      [1913 Webster]
   2. Exciting laughter; worthy to be laughed at; amusing.
      "Risible absurdities." --Johnson.
      [1913 Webster]
            I hope you find nothing risible in my complaisance.
                                                  --Sir W.
                                                  Scott.
      [1913 Webster]
   3. Used in, or expressing, laughter; as, risible muscles.
      [1913 Webster]
   Note: Risible is sometimes used as a noun, in the plural, for
         the feeling of amusement and for the muscles and other
         organs used in laughing, collectively; as, unable to
         control one's risibles.
         [1913 Webster]
   Syn: Ludicrous; laughable; amusing; ridiculous -- Risible,
        Ludicrous, Ridiculous.
   Usage: Risible differs from ludicrous as species from genus;
          ludicrous expressing that which is playful and
          sportive; risible, that which may excite laughter.
          Risible differs from ridiculous, as the latter implies
          something contemptuous, and risible does not.
          [1913 Webster] --Ris"i*ble*ness, n. -- Ris"i*bly,
          adv.
          [1913 Webster]
WordNet (r) 3.0 (2006):
risible
    adj 1: arousing or provoking laughter; "an amusing film with a
           steady stream of pranks and pratfalls"; "an amusing
           fellow"; "a comic hat"; "a comical look of surprise";
           "funny stories that made everybody laugh"; "a very funny
           writer"; "it would have been laughable if it hadn't hurt
           so much"; "a mirthful experience"; "risible courtroom
           antics" [syn: amusing, comic, comical, funny,
           laughable, mirthful, risible]
Moby Thesaurus II by Grady Ward, 1.0:
36 Moby Thesaurus words for "risible":
   absurd, amusing, bizarre, buxom, comic, comical, droll, eccentric,
   farcical, frivolous, funny, gleeful, hilarious, humorous,
   incongruous, jocular, jocund, jolly, jovial, joyful, joyous,
   laughable, laughter-loving, ludicrous, merry, mirth-loving,
   mirthful, priceless, quaint, quizzical, rejoicing, rich,
   ridiculous, screaming, whimsical, witty