having a defect or flaw; faulty; imperfect

a defective machine.

Psychology . characterized by subnormal intelligence or behavior.

Grammar . (of an inflected word or its inflection) lacking one or more of the inflected forms proper to most words of the same class in the language, as English must, which occurs only in the present tense.

a defective person or thing.

adjective

excellent , faultless , flawless , perfect , unbroken

adjective

abnormal , amiss , blemished , damaged , deficient , faulty , flawed , impaired , imperfect , inadequate , incomplete , injured , insufficient , lacking , on the bum , out of order , poor , seconds , sick , subnormal , unfinished , unhealthy , unsound , wantingnotes:defective means having a defect or fault , while deficient means inadequate or lacking in amount or degree , wanting