Synonyms for Involuntary (same or very similar meaning)
WordNet sense 1 (without volition or conscious control):
automatic
WordNet sense 2 (in spite of contrary volition):
unwilling
WordNet sense 3 (without conscious volition):
unconscious
WordNet sense 4 (forced or compelled):
forced
WordNet sense 5 (not subject to the control of the will):
nonvoluntary, unvoluntary
From the ODE community, based on WordNet
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