Definition of deficient adjective from the Oxford Advanced Learner's Dictionary



    BrE BrE//dɪˈfɪʃnt//
    ; NAmE NAmE//dɪˈfɪʃnt//
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  1. 1deficient (in something) not having enough of something, especially something that is essential a diet that is deficient in vitamin A Their food is deficient in iron. Your diet is deficient in iron.
  2. 2not good enough Deaf people are sometimes treated as being mentally deficient.
  3. Word Originlate 16th cent. (originally in the theological phrase deficient cause, denoting a failure or deficiency that has a particular consequence): from Latin deficient- ‘failing’, from the verb deficere ‘desert or fail’, from de- (expressing reversal) + facere ‘do’.
See the Oxford Advanced American Dictionary entry: deficient