What is verbalized?

Some articles on verbalized:

Snoopy - Character
... for the first two years of his existence, but on May 27, 1952 he verbalized his thoughts to readers for the first time in a thought balloon Schulz ... specials, Snoopy's thoughts are not verbalized his moods are instead conveyed through growls, sobs, laughter, and monosyllabic utterances such as "bleah," "hey," etc ... and Snoopy!!! The Musical, in which Snoopy's thoughts are verbalized through voice overs (by Robert Towers and Cam Clarke, respectively) ...