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.

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

That moment came courtesy of a guy wearing a Cubs uniform, but Monday grew up in Santa Monica and delivered his spontaneous commemoration of Flag Day in the year of America’s bicentennial.

From Los Angeles Times • Apr. 19, 2026

I thought of theory number five: spontaneous combustion.

From "The London Eye Mystery" by Siobhan Dowd

Vocabulary lists containing spontaneous

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