Webster's Revised Unabridged Dictionary · 1913

Risible

Risible , adjective

[French, from Latin risibilis, from ridere, risum, to laugh. Compare Ridiculous.]

1.
Having the faculty or power of laughing; disposed to laugh.
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. — Sir W. Scott
3.
Used in, or expressing, laughter; as, risible muscles.

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.