The Collaborative International Dictionary of English v.0.48:

Shrinkage \Shrink"age\, n.
   1. The act of shrinking; a contraction into less bulk or
      measurement.
      [1913 Webster]

   2. The amount of such contraction; the bulk or dimension lost
      by shrinking, as of grain, castings, etc.
      [1913 Webster]

   3. Decrease in value; depreciation. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

shrinkage
    n 1: process or result of becoming less or smaller; "the
         material lost 2 inches per yard in shrinkage" [syn:
         shrinking, shrinkage]
    2: the amount by which something shrinks
    3: the act of stealing goods that are on display in a store;
       "shrinkage is the retail trade's euphemism for shoplifting"
       [syn: shoplifting, shrinkage]