Antonyms for grave

crucial, dangerous:

little, small, insignificant.

serious; gloomy:

light, funny, boisterous, cheerful, trivial, frivolous, ridiculous, happy, unimportant, inconsequential, agitated, lively, excited, silly.

noun:

penetrating, strident, joking, Peeping, Weak-minded, screwball, trivial, nutty, loony, noncrucial, insignificant, beneficial, tinny, jerky, asinine, zany, sharp, insane, small, wacky, mad, witless, absurd, dotty, high, crazy, noncritical, balmy, little, senseless, unwise, piping, half-witted, cockeyed, slight, Daffy, foolish, advantageous, acute, brainless, safe, preposterous, uproarious, nonsensical, fatuous, daft, nonhazardous, sappy, kittenish, unthreatening, harmless, innocuous, minor, light, piercing, kooky, high-pitched, unserious, good, thin, innocent, hilarious, jesting, lite, cuckoo, squealing, earsplitting, lunatic.