To make sound with your voice. It covers more than speaking: a baby who is not yet talking vocalizes, a dog or a bird vocalizes, a singer vocalizes when warming up. The word cares about the voice being used, not about words being formed. There is a second, very common use that students meet more often: to vocalize a feeling or an opinion means to put it into words out loud instead of keeping it inside — "he never vocalizes what he wants". In that use it is close to "express" or "say", but it carries a hint that the thing was hard to say, or had been silent until now. You hear it in workplaces, therapy, and advice-giving. Both uses are somewhat formal; in casual talk people say "make a noise" or "speak up". Britain often spells it "vocalise".

發出聲音、出聲；把（想法、感受）說出口