The Collaborative International Dictionary of English v.0.48:

Taster \Tast"er\ (t[=a]st"[~e]r), n.
   1. One who tastes; especially, one who first tastes food or
      drink to ascertain its quality.
      [1913 Webster]

            Thy tutor be thy taster, ere thou eat. --Dryden.
      [1913 Webster]

   2. That in which, or by which, anything is tasted, as, a dram
      cup, a cheese taster, or the like.
      [1913 Webster]

   3. (Zool.) One of a peculiar kind of zooids situated on the
      polyp-stem of certain Siphonophora. They somewhat resemble
      the feeding zooids, but are destitute of mouths. See
      Siphonophora.
      [1913 Webster]

WordNet (r) 3.0 (2006):

taster
    n 1: someone who samples food or drink for its quality [syn:
         taster, taste tester, taste-tester, sampler]