1. Relating to the period before a child learns to speak. This is the most common meaning. For example, you might hear someone talk about "preverbal communication" in infants, referring to the ways they communicate before they can use words, such as through facial expressions, gestures, and sounds.
2. Occurring before a verb in a sentence. This meaning is less common and mainly used in linguistic contexts. For example, an adverb placed before a verb is considered "preverbal".
In both cases, the key element is "before" something related to language.
Let me know if you'd like more examples or explanation!