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.

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

From Barron's • May 21, 2026

In 2024, for example, more than 700 newborns died from spontaneous bleeding in their brains, which could have been complicated by liver disease or prematurity.

From Salon • May 7, 2026

Shapiro wants to bring back the spontaneous phone call.

From The Wall Street Journal • May 1, 2026

“It’s spontaneous combustion,” said James Boles, a professor emeritus with UC Santa Barbara’s Earth Science Department.

From Los Angeles Times • Apr. 24, 2026

Whether her outpouring in front of Czarnecki was the spontaneous result of having reached a breaking point or something more astute, she picked the right person to vent to.

From "Hidden Figures" by Margot Lee Shetterly

Vocabulary lists containing spontaneous

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