absurd, cockamamy(or cockamamie), comical, derisory, farcical, laughable, ludicrous, pathetic, preposterous, ridiculous, risible, silly

asinine, brainless, dumb, fatuous, foolish, half-baked, half-witted, harebrained, idiotic(also idiotical), imbecile(or imbecilic), inane, jerky, moronic, nonsensical, simpleminded, stupid, unwise, weak-minded, witlessbalmy, cockeyed, crazy, cuckoo, daffy, daft, dotty, insane, kooky(also kookie), loony(also looney), lunatic, mad, nutty, screwball, senseless, wacky(also whacky)fantastic(also fantastical), far-fetched, inconceivable, incredible, unbelievable, unreal, unrealistic, unreasonableillogical, irrational

for the birds