The Collaborative International Dictionary of English v.0.48:

Anneal \An*neal"\, v. t. [imp. & p. p. Annealed; p. pr. & vb.
   n. Annealing.] [OE. anelen to heat, burn, AS. an?lan; an on
   + ?lan to burn; also OE. anelen to enamel, prob. influenced
   by OF. neeler, nieler, to put a black enamel on gold or
   silver, F. nieller, fr. LL. nigellare to blacken, fr. L.
   nigellus blackish, dim. of niger black. Cf. Niello,
   Negro.]
   1. To subject to great heat, and then cool slowly, as glass,
      cast iron, steel, or other metal, for the purpose of
      rendering it less brittle; to temper; to toughen.
      [1913 Webster]

   2. To heat, as glass, tiles, or earthenware, in order to fix
      the colors laid on them.
      [1913 Webster]

WordNet (r) 3.0 (2006):

anneal
    v 1: bring to a desired consistency, texture, or hardness by a
         process of gradually heating and cooling; "temper glass"
         [syn: anneal, temper, normalize]