Synonyms for Risible:

adj.

amusing (adjective)
comical.
humorous (adjective)
droll, comical, funny, amusing, laughable.

n.

insane, childish, crazy, laughter, mad, over-the-top, zany, not in your right mind/not right in the head, droll. laughing, farcical. risible (noun)
amusing, comical, humourous, humorous, mirthful, comic, funny, laughable.

Other synonyms:

laughing, farcical, zany, droll. Other relevant words:
childish, droll, laughing, insane, zany, crazy, farcical, mad.