The Collaborative International Dictionary of English v.0.48:

Shortage \Short"age\, n.
   Amount or extent of deficiency, as determined by some
   requirement or standard; as, a shortage in money accounts.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shortage
    n 1: the property of being an amount by which something is less
         than expected or required; "new blood vessels bud out from
         the already dilated vascular bed to make up the nutritional
         deficit" [syn: deficit, shortage, shortfall]
    2: an acute insufficiency [syn: dearth, famine, shortage]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "shortage":
   absence, adulteration, arrear, arrearage, arrears, beggary, break,
   curtailment, dearth, decline, defalcation, default, defect,
   defectibility, defectiveness, deficiency, deficit, delinquency,
   deprivation, destitution, discontinuity, drought, erroneousness,
   failure, fallibility, falling short, famine, faultiness, gap,
   hiatus, immaturity, impairment, imperfection, impoverishment,
   impurity, inaccuracy, inadequacy, inadequateness, incompleteness,
   inexactitude, inexactness, inferiority, insufficiency, interval,
   lack, lacuna, mediocrity, missing link, need, omission, outage,
   patchiness, paucity, pinch, scantiness, scarcity, short measure,
   shortcoming, shortfall, sketchiness, slump, starvation, tightness,
   ullage, underage, undevelopment, unevenness, unperfectedness,
   unsoundness, want, wantage