Harebrained

Adjective

 * 1)  absurd, foolish or stupid
 * 2)  frivolous and silly; featherbrained or scatterbrained

Thesaurus
absurd, adventurous, arbitrary, audacious, balmy, bold, brainless, capricious, cranky, crazy, crotchety, daredevil, daring, death-defying, dizzy, empty-headed, fanciful, fantasied, fantastic, featherbrained, featherheaded, fire-eating, flaky, flighty, fluttery, foolhardy, forward, freakish, frivolous, gaga, giddy, giddy-brained, giddy-headed, giddy-pated, giddy-witted, harebrain, humorsome, insane, kinky, loony, madbrain, madbrained, madcap, maggoty, moody, motiveless, notional, petulant, potty, preposterous, presumptuous, quirky, rattlebrained, rattleheaded, rattlepated, scatterbrained, scramblebrained, shatterbrained, silly, skittish, temperamental, thoughtless, unreasonable, unrestrained, vagarious, vagrant, wacky, wanton, wayward, whimsical, wild, wild-ass, witless

Alternative forms

 * hare-brained