The Collaborative International Dictionary of English v.0.48:

Prologize \Pro"lo*gize\, v. i. [Gr. ?. See Prologue.]
   To deliver a Prologue. [R.] --Whewell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prologize
    v 1: write or speak a prologue [syn: prologize, prologuize,
         prologise]