Definitions

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.

Made with soft, cushiony materials, the doll also makes spontaneous requests, asking users to pat its head, hold its hand or share snacks with it, although it cannot eat.

From Barron's • Jun. 11, 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

Shapiro wants to bring back the spontaneous phone call.

From The Wall Street Journal • May 1, 2026

He probably ought to speak with Cantu, then, going over the facts so that the mayor would understand this incident was spontaneous, not planned—Pacheco had acted on his own.

From "The Milagro Beanfield War" by John Nichols

Vocabulary lists containing spontaneous

Essential Academic Vocabulary for High School Students, List 1

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100 Top "SAT" Words

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Animal Farm

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