erratic

American  

[ih-rat-ik] / ɪˈræt ɪk /

adjective

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

   erratic behavior.

   Synonyms:

   capricious, unstable, unpredictable

   Antonyms:

   stable, regular, consistent

2. inconsistent, irregular, or unpredictable.

   Many factors affect purchasing power, such as inflation and erratic swings in the stock market.

3. having no certain or definite course or pattern; wandering; not fixed.

   erratic winds.

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

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

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noun

1. an erratic or eccentric person.

2. Geology. an erratic boulder or the like.

erratic British  

/ ɪˈrætɪk /

adjective

1. irregular in performance, behaviour, or attitude; inconsistent and unpredictable

2. having no fixed or regular course; wandering

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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

2. an erratic person or thing

Other Word Forms

• erratically adverb
• erraticism noun
• nonerratic adjective
• unerratic adjective

Etymology

Origin of erratic

First recorded in 1325–75; Middle English, from Latin errāticus, equivalent to errāt(us) (past participle of errāre “to make a mistake, err” ( see err) + -icus -ic

Explanation

The adjective erratic describes things that are unpredictable, unusual, and that deviate from the norm. An erratic quarterback might completely confuse his receivers waiting for a pass. Like its linguistic relative, error, the adjective erratic means "deviating from the norm," or "wrong." It also implies behavior or qualities that are unpredictable or odd. The word comes from the Latin verb errare, or "to wander" off course. In the field of geology, a rock that is erratic is unlike others in its environment because it has been transported by glacial activity. Likewise, someone driving a car that veers out of its lane is said to be driving erratically.

Example Sentences

His erratic messaging on Iran is further diluted by increasingly frequent digressions on his favorite topic: the construction and renovation of buildings.

From Barron's • Apr. 21, 2026

With high noise, their paths became erratic and inefficient.

From Science Daily • Apr. 15, 2026

Climate change is wreaking havoc on agriculture, bringing stronger storms, longer droughts, erratic rainfall and rising temperatures.

From Salon • Apr. 11, 2026

Their most important ally is acting in ways that they see as erratic and that have already caused hardship and uncertainty.

From The Wall Street Journal • Apr. 7, 2026

The Greek never got on to the erratic movements of the knights and the sweeping mobility of the queens, but he learned to make a few set, opening moves.

From "The Heart is a Lonely Hunter" by Carson McCullers

Related Words

• abnormal
• arbitrary
• bizarre
• capricious
• eccentric
• inconsistent
• irregular
• mercurial
• uncertain
• unreliable
• unstable
• unusual
• volatile
• wayward
• weird
• whimsical