adj. 1
Without intention; unintentional.
adj. 2
Not voluntary or willing; contrary or opposed to explicit will or desire; unwilling.
He found himself the involuntary witness in the trial.

Related words

Word family: involuntariness
Phrases: involuntary muscle

Choose the right word

Involuntary, Voluntary, Spontaneous, Unbidden or Willing?

Thus voluntary and involuntary, which are antonyms of each other, are both partial synonyms of spontaneous. We speak of spontaneous generation, spontaneous combustion, spontaneous sympathy, an involuntary start, an unbidden tear, voluntary agreement, willing submission.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

forced Circumstances forced us to cancel our appointment.
compulsory In Algeria, it's not compulsory to wear the hijab.
automatic Most workers get an automatic pay raise every year.
unconscious I don't know what happened when I was unconscious.
uncontrollable I am seized by an uncontrollable wave of sadness.

Popularity over time

Word	1850 → 2019	Trend
involuntary		steady
forced		rising
compulsory		falling
inadvertent		steady
automatic		falling
unconscious		rising

Use in printed books, per decade from 1850 to 2019.

By length

5 letters: blind¹
6 letters: forced¹, reflex²
8 letters: unwilled
9 letters: necessary⁴, automatic⁴, mandatory⁴, unwilling³, reflexive³, unwitting³, unbewised
10 letters: mechanical⁴, compulsory⁴, unintended⁴, unpurposed
11 letters: unconscious³, instinctive³, inadvertent⁴, unvoluntary
12 letters: nonvoluntary, unvolitional
13 letters: unintentional⁵
14 letters: uncontrollable⁵

The small number after each word is its number of syllables (reflex² = 2 syllables).

In other languages

Français: involontaire
Deutsch: versehentlich