deviating from the usual or proper course in conduct or opinion; eccentric; queer

erratic behavior.

having no certain or definite course; wandering; not fixed

erratic winds.

Geology . noting or pertaining to a boulder or the like carried by glacial ice and deposited some distance from its place of origin.

(of a lichen) having no attachment to the surface on which it grows.

an erratic or eccentric person.

Geology . an erratic boulder or the like.

adjective

certain , consistent , definite , dependable , predictable , regular , reliable , steady , sure , unchanging

adjective

aberrant , abnormal , anomalous , arbitrary , bizarre , capricious , changeable , desultory , devious , dicey , directionless , dubious , eccentric , fitful , flaky * , fluctuant , idiosyncratic , iffy * , incalculable , inconsistent , inconstant , irregular , meandering , mercurial , nomadic , oddball * , peculiar , planetary , rambling , roving , shifting , spasmodic , strange , stray , uncertain , undirected , unnatural , unreliable , unstable , unusual , vagarious , variable , volatile , wayward , weird , whimsical , wandering , patchy , spotty , unsteady , fantastic , fantastical , fickle , freakish , temperamental , ticklish , unpredictable , cranky , curious , odd , outlandish , quaint , queer , quirky , singular , circuitous , errant , fallible , fanciful , tangential , vagrant , wacky , wild