hilarious

Definitions:

Gay; mirthful.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (adjective) (adj.) (adjective)
Merry; exhilarated; noisy; mirthful; jolly; boisterous; as, hilarious merriment.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (adjective) (adj.) (adjective)
Mirthful; merry.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (adjective) (adj.) (adjective)
hilariously.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (adverb) (adv.) (adverb)
Gay: very merry.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (adjective) (adj.) (adjective)

Usage examples:

They wouldn't be so hilarious if it were their own households they were setting topsy- turvy; if they had sixteen " place- cards" yet to finish.
- Missy by Dana Gatlin
Tom didn't feel unduly hilarious however.
- Left End Edwards by Ralph Henry Barbour
I thank them for recalling my attention to a truth which I shall be wiser, if not more hilarious for remembering.
- A Mortal Antipathy by Oliver Wendell Holmes, Sr.