The Collaborative International Dictionary of English v.0.48:

Baptize \Bap*tize"\, v. t. [imp. & p. p. Baptized; p. pr. &
   vb. n. Baptizing.] [F. baptiser, L. baptizare, fr. Gr.
   bapti`zein. See Baptism.]
   1. To administer the sacrament of baptism to.
      [1913 Webster]

   2. To christen (because a name is given to infants at their
      baptism); to give a name to; to name.
      [1913 Webster]

            I'll be new baptized;
            Henceforth I never will be Romeo.     --Shak.
      [1913 Webster]

   3. To sanctify; to consecrate.
      [1913 Webster]

WordNet (r) 3.0 (2006):

baptized
    adj 1: having undergone the Christian ritual of baptism [syn:
           baptized, baptised] [ant: unbaptised, unbaptized]