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.
a. - Lacking some of the usual forms of declension or conjugation; as, a defective noun or verb.
n. - Anything that is defective or lacking in some respect.
n. - One who is lacking physically or mentally.