spontaneous

[spon-tey-nee-uhs] / spɒnˈteɪ ni əs /

ADJECTIVE

impulsive, willing

Synonyms

STRONGEST

casual impromptu instinctive offhand simple unplanned voluntary

WEAK

ad-lib automatic break loose down extemporaneous extempore free free-spirited from the hip impetuous improvised inevitable involuntary irresistible natural off top of head off-the-cuff unartful unavoidable unbidden uncompelled unconscious unconstrained uncontrived uncontrolled unforced unintentional unpremediated unprompted unsophisticated unstudied up front

Antonyms

STRONGEST

deliberate planned

WEAK

intended premeditated

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

He took up the spontaneous change in assignment because he "wanted to earn some extra money", HTA manager Angfurba Sherpa tells the BBC.

From BBC • Jun. 10, 2026

Most cancers are spontaneous and can’t be detected in a genetic test.

From Barron's • May 21, 2026

They also showed stronger protection against spontaneous tumors and chemically induced skin cancer.

From Science Daily • May 10, 2026

“She had a spontaneous unexplained brain bleed that led to brain death.”

From Salon • May 7, 2026

If we bring it close to the uranium ore, which is emitting helium nuclei in a spontaneous nuclear decay, the count rate, the number of clicks per minute, increases dramatically.

From "Cosmos" by Carl Sagan

Vocabulary lists containing spontaneous

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