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

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

From Salon • May 7, 2026

I’m batting about .500 in my attempt to revive the spontaneous call.

From The Wall Street Journal • May 1, 2026

Our first clue that this leave-taking lies somewhere between planned and spontaneous is in Martin’s gently charged response in answer to his daughter’s initial confusion: What would you take if the house were on fire?

From Los Angeles Times • May 1, 2026

This theory of spontaneous generation had ancient origins and lingered until the early 1700s.

From "The Girl Who Drew Butterflies: How Maria Merian's Art Changed Science" by Joyce Sidman

Vocabulary lists containing spontaneous

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