Meaning of DEFICIENT in English
/ dɪˈfɪʃnt; NAmE / adjective
deficient (in sth) not having enough of sth, especially sth that is essential :
a diet that is deficient in vitamin A
( formal ) not good enough :
Deaf people are sometimes treated as being mentally deficient.
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.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005