adrift afloat alternating amorphous blank brainless capricious changeable changeful dazed desultory deviable dippy dizzy dopey eccentric empty empty-headed empty-minded empty-pated empty-skulled erratic fast and loose featherbrained featherheaded fickle fitful flibbertigibbet flickering flighty flitting fluctuating fluttery freakish frivolous gaga giddy giddy-brained giddy-headed giddy-pated giddy-witted harebrain harebrained hollow impetuous impulsive inane inconsistent inconstant indecisive infirm irregular irresolute irresponsible jejune mazy mercurial moody rambling rattlebrained rattleheaded rattlepated restless roving scramblebrained shapeless shatterbrained shifting shifty shuffling silly spasmodic spineless thoughtless unaccountable uncertain uncontrolled undependable undisciplined unfixed unpredictable unreliable unrestrained unsettled unstable unstable as water unstaid unsteadfast unsteady vacant vacillating vacuous vagrant vapid variable vicissitudinary vicissitudinous volatile wandering wanton wavering wavery wavy wayward whimsical wishy-washy witless