malfunctioning
mal-func-tion-ing
adjective
Not working correctly or failing to operate as intended.
"The malfunctioning printer needed repair."
verb
The act or process of failing to work or operate correctly.
"Engineers investigated the system malfunctioning."
Thesaurus
Synonyms: nonfunctional, haywire, wrong, run-down, awry, defective, out of whack, bad, amiss
Antonyms: functioning