The Collaborative International Dictionary of English v.0.48:
Hilarious \Hi*la"ri*ous\, a. [L. hilaris, hilarus, Gr. ?; cf. ? gracious, kindly.] Mirthful; noisy; merry. [1913 Webster]WordNet (r) 3.0 (2006):
hilarious adj 1: marked by or causing boisterous merriment or convulsive laughter; "hilarious broad comedy"; "a screaming farce"; "uproarious stories" [syn: hilarious, screaming(a), uproarious]