mid-14c., from Middle French défectif (14c.) and directly from Late Latin defectivus, from defect-, past participle stem of deficere (see deficient). A euphemism for "mentally ill" from 1898 to c. 1935. Related: Defectively; defectiveness.
1. A manufacturer negligently made and marketed a car with defective brakes.
2. Retailers can return defective merchandise.
3. Her sight was becoming defective.
4. Her hearing was found to be slightly defective.
5. The building was destroyed when the defective boiler exploded.