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1. Not performing or able to perform its regular function
   "a malfunctioning valve"
   - nonfunctional

1. Fail to function or function improperly
   "the coffee maker malfunctioned"
   - misfunction

See also: amiss, awry, bad, defective, haywire, out of whack, run-down, wrong

Type of: break, break down, conk out, die, fail, give out, give way, go, go bad

Antonym: function, functioning

Encyclopedia: Malfunction