Source : Webster's Revised Unabridged Dictionary (1913)

Externalize \Ex*ter"nal*ize\, v. t.
   To make external; to manifest by outward form.

         Thought externalizes itself in language. --Soyce.

Source : WordNet®

externalize
     v 1: regard as objective [syn: {project}, {externalise}]
     2: make external or objective, or give reality to; "language
        externalizes our thoughts" [syn: {exteriorize}, {exteriorise},
         {externalise}, {objectify}]