I. di-ˈfi-shənt adjective
Etymology: Latin deficient-, deficiens, present participle of deficere to be wanting — more at defect
Date: 1581
1. : lacking in some necessary quality or element
deficient in judgment
2. : not up to a normal standard or complement : defective
deficient strength
• de·fi·cient·ly adverb
II. noun
Date: 1906
: one that is deficient
a mental deficient