/ dɪˈfɪʃnt; NAmE / adjective
1.
deficient (in sth) not having enough of sth, especially sth that is essential :
a diet that is deficient in vitamin A
2.
( formal ) not good enough :
Deaf people are sometimes treated as being mentally deficient.
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WORD ORIGIN
late 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.