The Collaborative International Dictionary of English v.0.48:

Risibility \Ris`i*bil"i*ty\, n. [CF. F. risibilit['e].]
   The quality of being risible; as, risibility is peculiar to
   the human species.
   [1913 Webster]

         A strong and obvious disposition to risibility. --Sir
                                                  W. Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

risibility
    n 1: a disposition to laugh

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "risibility":
   Homeric laughter, belly laugh, boff, boffola, burst of laughter,
   cachinnation, cackle, chortle, chuckle, convulsion, crow,
   fit of laughter, funny bone, gales of laughter, giggle, guffaw,
   ha-ha, hearty laugh, hee-haw, hee-hee, hilarity, ho-ho, horselaugh,
   laugh, laughing, laughter, outburst of laughter, peal of laughter,
   roar of laughter, sense of humor, shout, shout of laughter, shriek,
   snicker, snigger, snort, tee-hee, titter, yuck, yuk-yuk