The Oxford Thesaurus An A-Z Dictionary of Synonyms - silly adj.

1) senseless, nonsensical, absurd, ridiculous, ludicrous, laughable, risible, asinine, inane, preposterous, idiotic, childish, puerile, foolish, foolhardy, irresponsible, unreasonable, illogical, irrational, pointless, fatuous, stupid, unwise, imbecilic, crazy, mad, insane: It would be silly to pay for it if you can get it for nothing. 2) stunned, stupefied, daze, giddy, dizzy, muzzy, benumbed: Culley said something rude and the girl knocked him silly with a karate chop. --n. 3) fool, nincompoop, idiot, dunce, ninny, halfwit, simpleton, numskull or numbskull, dim-wit, booby, dolt, jackass, twit, dolt, blockhead, bonehead, nitwit, ignoramus, clod, US thimble-wit, Colloq dope, dummy, knuckle-head, goose, drip, silly billy, Brit clot, Slang US and Canadian jerk, nerd: Warren is such a silly to spend so much money on a girl who cares nothing for him.