1. (a.) Fleeting; swift; transient.

2. (a.) Indulging in flights, or wild and unrestrained sallies, of imagination, humor, caprice, etc.; given to disordered fancies and extravagant conduct; volatile; giddy; eccentric; slightly delirious.

abnormal adrift afloat alternating amorphous bereft of reason birdbrained birdwitted brainsick buoyant capricious changeable changeful coquettish crackbrained cracked crazed crazy daft deluded demented deprived of reason deranged desultory deviable dippy disoriented distraught dizzy dotty eccentric effervescent empty-headed erratic faddish fanciful fast and loose featherbrained fickle fitful flickering flirtatious flitting fluctuating fluffy freakish frivolous frothy gay giddy hallucinated harebrained impetuous impulsive inconsistent inconstant indecisive infirm insane irrational irregular irresolute irresponsible light light-headed lively loco lunatic mad maddened manic mazed mazy mental mentally deficient mercurial meshuggah moody moon-struck non compos non compos mentis not all there not right nutty odd of unsound mind off psycho queer quicksilver rambling rattlebrained reasonless reckless restless roving scatterbrained screwy senseless shallow shallow-headed shallow-minded shallow-pated shallow-witted shapeless shifting shifty shuffling sick silly skittish spasmodic spineless sprightly stark-mad stark-staring mad strange superficial tetched thoughtless touched toying unaccountable unbalanced uncertain uncontrolled undependable undisciplined unfixed unhinged unpredictable unprofound unreliable unrestrained unsane unsettled unsound unstable unstable as water unstaid unsteadfast unsteady vacillating vagrant variable versatile vicissitudinary vicissitudinous volatile wandering wanton wavering wavery wavy wayward whimsical wild wishy-washy witless