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 [informal], die, fail, give out, give up the ghost [informal], give way, go, go bad, pack up [Brit, informal]

Antonym: function, functioning

Encyclopedia: Malfunctioning