What do vi and vt mean in definitions found dictionaries?

You're likely referring to vi and vt in dictionary entries, which stand for:

* vi: Verb Intransitive - This means the verb does not take a direct object. The action of the verb is complete within itself, without affecting a noun or pronoun.

* Example: "The bird sings." (The bird is performing the action of singing, but there's no direct object being acted upon.)

* vt: Verb Transitive - This means the verb requires a direct object to complete its meaning. The action of the verb is directed toward a noun or pronoun.

* Example: "The boy kicked the ball." (The verb "kicked" requires the direct object "ball" to make sense. The boy is performing the action of kicking, and the ball is the object being acted upon.)

Let me know if you'd like more examples or have any other dictionary abbreviations you'd like explained!