erratic

UK: /ɪˈrætɪk/ US: /ɪˈrætɪk/ ,(i rat′ik)

WordReference Random House Learner's Dictionary of American English © 2026

er•rat•ic /ɪˈrætɪk/   adj. 

1. changeable in behavior or style;
   unpredictable:
   behavior too erratic to trust.

er•rat•i•cal•ly, adv. 

WordReference Random House Unabridged Dictionary of American English © 2026

er•rat•ic  (i rat′ik), adj. 

1. deviating from the usual or proper course in conduct or opinion;
   eccentric;
   queer:
   erratic behavior.
2. having no certain or definite course;
   wandering;
   not fixed:
   erratic winds.
3. Geology noting or pertaining to a boulder or the like carried by glacial ice and deposited some distance from its place of origin.
4. Fungi (of a lichen) having no attachment to the surface on which it grows.

n. 

5. an erratic or eccentric person.
6. Geology an erratic boulder or the like.

• Latin errāticus, equivalent. to errāt(us) (past participle of errāre to err) + -icus -ic
• Middle English 1325–75

er•rat′i•cal•ly, adv. 
er•rat′i•cism, n. 
Synonyms

• 1. unpredictable, unstable, capricious.

Antonyms

• 1. consistent, regular, stable.

Collins Concise English Dictionary © HarperCollins Publishers::

erratic / ɪˈrætɪk/ adjective
also: erratical

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

noun

1. 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

Etymology: 14th Century: from Latin errāticus, from errāre to wander, err

erˈratically adverb