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

Derived Forms

• erraticism
  noun
• erratically
  adverb
• 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

The company blamed the increase on erratic weather that created more dried vegetation.

From Los Angeles Times • Jun. 9, 2026

While astronomers and space scientists were initially skeptical about the planet nine theory, there has been mounting evidence thanks to increasingly powerful observations that the orbits of trans-Neptunian objects are indeed erratic.

From Science Daily • Jun. 9, 2026

These erratic financial operations which are very large relative to Ireland's domestic economy thus generate heightened volatility in national and European statistics.

From Barron's • Jun. 5, 2026

The court heard that Parker's behaviour had become "erratic" and he refused repeated attempts by his mother and sister to persuade him to get mental health support.

From BBC • May 22, 2026

The weather in Washington, DC, can be erratic, especially in winter.

From "Votes for Women!" by Winifred Conkling

Related Words

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