Source : Webster's Revised Unabridged Dictionary (1913)

Deficit \Def"i*cit\, n. [Lit., it is wanting, 3d person pres.
   indic. of L. deficere, cf. F. d['e]ficit. See {Defect}.]
   Deficiency in amount or quality; a falling short; lack; as, a
   deficit in taxes, revenue, etc. --Addison.

Source : WordNet®

deficit
     n 1: the property of being an amount by which something is less
          than expected or required [syn: {shortage}, {shortfall}]
     2: an excess of liabilities over assets (usually over a certain
        period)