Defective

adj. imperfect; deficient, lacking

Defective can mean multiple things:anything with a defectin algebra, a defective matrixin linguistics, a defective verb
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Adjective
1. having a defect; "I returned the appliance because it was defective"
(synonym) faulty
(similar) imperfect
2. markedly subnormal in structure or function or intelligence or behavior; "defective speech"
(similar) abnormal
3. not working properly; "a bad telephone connection"; "a defective appliance"
(synonym) bad
(similar) malfunctioning, nonfunctional

adj. defective, imperfect

(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.