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.

Origin of erratic

1325–75; Middle English < Latin errāticus, equivalent to errāt(us) (past participle of errāre to err) + -icus -ic
Related formser·rat·i·cal·ly, adverber·rat·i·cism, nounnon·er·rat·ic, adjective, nounnon·er·rat·i·cal·ly, adverbun·er·rat·ic, adjective
Can be confusederotic erratic exotic

Synonyms for erratic

Antonyms for erratic Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for erratic

Contemporary Examples of erratic

Historical Examples of erratic

  • He worked in his erratic way all winter, and certainly did have some success.

    Johnny Bear

    E. T. Seton

  • With them we think of the artificial as the archetype; the earth-born as the erratic exception.

    Alarms and Discursions

    G. K. Chesterton

  • Calhoun swung it on an erratic course, lest there be opposition.

    Pariah Planet

    Murray Leinster

  • Susan, holding on against the erratic swayings of the cart, pretended not to hear.

    Tales of Unrest

    Joseph Conrad

  • Sam was volatile and elusive; his industry of an erratic kind.

British Dictionary definitions for erratic



irregular in performance, behaviour, or attitude; inconsistent and unpredictable
having no fixed or regular course; wandering


a piece of rock that differs in composition, shape, etc, from the rock surrounding it, having been transported from its place of origin, esp by glacial action
an erratic person or thing
Derived Formserratically, adverb

Word Origin for erratic

C14: from Latin errāticus, from errāre to wander, err
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for erratic

late 14c., "wandering, moving," from Old French erratique (13c.) and directly from Latin erraticus "wandering, straying, roving," from erratum "an error, mistake, fault," past participle of errare "to wander, err" (see err). Sense of "irregular, eccentric" is attested by 1841. The noun is from 1620s, of persons; 1849, of boulders. Related: Erratically.

Online Etymology Dictionary, © 2010 Douglas Harper