Source : Webster's Revised Unabridged Dictionary (1913)

Deficiency \De*fi"cien*cy\, n.; pl. {Deficiencies}. [See
   {Deficient}.]
   The state of being deficient; inadequacy; want; failure;
   imperfection; shortcoming; defect. ``A deficiency of blood.''
   --Arbuthnot.

         [Marlborough] was so miserably ignorant, that his
         deficiencies made him the ridicule of his
         contemporaries.                          --Buckle.

   {Deficiency of a curve} (Geom.), the amount by which the
      number of double points on a curve is short of the maximum
      for curves of the same degree.

Source : WordNet®

deficiency
     n 1: the state of needing something that is absent or
          unavailable; "there is a serious lack of insight into
          the problem"; "water is the critical deficiency in
          desert regions"; "for want of a nail the shoe was lost"
          [syn: {lack}, {want}]
     2: lack of an adequate quantity or number; "the inadequacy of
        unemployment benefits" [syn: {insufficiency}, {inadequacy}]
        [ant: {sufficiency}, {sufficiency}]