Let's break down some possibilities:
* You might be thinking about "defining verb": This is a verb that defines the action of a sentence. It's the main verb, often describing what the subject is doing. Example: "The dog ran quickly." ("ran" is the defining verb)
* You might be thinking about "transitive verb": These verbs take a direct object. The action of the verb is performed on something. Example: "She wrote a letter." ("wrote" is transitive; the object is "letter")
* You might be thinking about "auxiliary verb": These verbs help the main verb express tense, mood, or voice. They come before the main verb. Example: "I am reading a book." ("am" is the auxiliary verb; "reading" is the main verb)
* You might be thinking about "modal verb": These verbs modify another verb, expressing possibility, ability, obligation, etc. Examples: "I can swim." "He should study."
If you can provide more context or an example sentence, I can help you identify the specific verb type you're looking for.