Wanting either in substance, quantity or quality, or in any thing necessary; imperfect; as a defective limb; defective timber; a defective copy or book; a defective account. Defective articulation, in speaking, renders utterance indistinct.

Wanting in moral qualities; faulty; blamable; not conforming to rectitude or rule; as a defective character.

In grammar, a defective noun is one which wants a whole number or a particular case; an indeclinable noun.

A defective verb, is one which wants some of the tenses.