The Collaborative International Dictionary of English v.0.48:

Anagrammatize \An`a*gram"ma*tize\, v. t. [Gr. 'anagrammati`zein
   cf. F. anagrammatiser.]
   To transpose, as the letters of a word, so as to form an
   anagram. --Cudworth.
   [1913 Webster]

WordNet (r) 3.0 (2006):

anagrammatize
    v 1: read letters out of order to discover a hidden meaning
         [syn: anagram, anagrammatize, anagrammatise]