defective

adjective

1 a defective seat belt:

faulty, flawed, imperfect, shoddy, inoperative, not working, not functioning, non-functioning, malfunctioning, out of order, unsound;

weak, deficient, incomplete;

in disrepair, broken, cracked, torn, scratched, deformed, warped, buckled;

informal gone wrong, on the blink;

British, informal knackered, duff.

▷antonyms working, perfect.

2 these methods are defective in strength and durability:

lacking, wanting, deficient, inadequate, insufficient, short, low, scant.

defective Oxford Dictionary of English