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]