The Collaborative International Dictionary of English v.0.48:

lexicalize \lex"i*cal*ize\ (l[e^]ks"[i^]*kal*[imac]z), v. t.
   1. To make into a word, coin into a word; as, The concept
      expressed by German "Gemuetlichkeit" is not lexicalized in
      English.
      [WordNet 1.5]

   2. To increase the importance of, or emphasis on, words as
      opposed to other parts of a theory or program; -- said of
      grammatical theories and computer programs, especially
      programs for understanding language; as, lexicalized
      tree-adjoining grammar.
      [PJC]

WordNet (r) 3.0 (2006):

lexicalize
    v 1: make or coin into a word or accept a new word into the
         lexicon of a language; "The concept expressed by German
         `Gemuetlichkeit' is not lexicalized in English" [syn:
         lexicalize, lexicalise]