(1):
(a.) Wanting in something; incomplete; lacking a part; deficient; imperfect; faulty; - applied either to natural or moral qualities; as, a defective limb; defective timber; a defective copy or account; a defective character; defective rules.
(2):
(a.) Lacking some of the usual forms of declension or conjugation; as, a defective noun or verb.
(3):
(n.) Anything that is defective or lacking in some respect.
(4):
(n.) One who is lacking physically or mentally.