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
Laughing is our busines, . . . it has been made the
definition of man that he is risible. --Dr. H. More.
2. Exciting laughter; worthy to be laughed at; amusing.
"Risible absurdities." --Johnson.
I hope you find nothing risible in my complaisance.
3. Used in, or expressing, laughter; as, risible muscles.
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.
Syn: Ludicrous; laughable; amusing; ridiculous -- Risible,
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,