DEFICIENT

deficient, lacking, wanting

(adjective) inadequate in amount or degree; “a deficient education”; “deficient in common sense”; “lacking in stamina”; “tested and found wanting”

deficient, inferior, substandard

(adjective) falling short of some prescribed norm; “substandard housing”

insufficient, deficient

(adjective) of a quantity not able to fulfill a need or requirement; “insufficient funds”

Source: WordNet® 3.1

Etymology

Adjective

deficient (comparative more deficient, superlative most deficient)

Lacking something essential; often construed with in.

Insufficient or inadequate in amount.

(mathematics) Of a number n, Having the sum of divisors σ(n)<2n, or, equivalently, the sum of proper divisors (or aliquot sum) s(n)

Source: Wiktionary

De*fi"cient, a. Etym: [L. deficiens, -entis, p. pr. of deficere to be wanting. See Defect.]

Definition: Wanting, to make up completeness; wanting, as regards a requirement; not sufficient; inadequate; defective; imperfect; incomplete; lacking; as, deficient parts; deficient estate; deficient strength; deficient in judgment. The style was indeed deficient in ease and variety. Macaulay. Deficient number. (Arith.) See under Abundant.

– De*fi"cient-ly, adv.

Source: Webster’s Unabridged Dictionary 1913 Edition