The Collaborative International Dictionary of English v.0.48:

Specialize \Spe"cial*ize\, v. t.
   1. To mention specially; to particularize.
      [1913 Webster]

   2. To apply to some specialty or limited object; to assign to
      a specific use; as, specialized knowledge.
      [1913 Webster]

   3. (Biol.) To supply with an organ or organs having a special
      function or functions.
      [1913 Webster]

WordNet (r) 3.0 (2006):

specialize
    v 1: become more focus on an area of activity or field of study;
         "She specializes in Near Eastern history" [syn:
         specialize, specialise, narrow, narrow down] [ant:
         branch out, broaden, diversify]
    2: be specific about; "Could you please specify your criticism
       of my paper?" [syn: specify, particularize,
       particularise, specialize, specialise] [ant:
       generalise, generalize]
    3: suit to a special purpose; "specialize one's research"; "this
       kind of beak has become specialized in certain Galapagos
       finches" [syn: specialize, specialise]
    4: devote oneself to a special area of work; "She specializes in
       honey bees"; "This baker specializes in French bread" [syn:
       specialize, specialise]
    5: evolve so as to lead to a new species or develop in a way
       most suited to the environment [syn: speciate,
       differentiate, specialize, specialise]