A transitive verb is a verb that requires a direct object to complete its meaning. In the given sentence, "Ring the bell twice," the verb "ring" is transitive because it acts on the direct object "the bell." The action of ringing is directed towards an object, making it a transitive verb. In contrast, intransitive verbs do not require a direct object and can stand alone. However, this sentence clearly has a direct object ("the bell"), confirming that "ring" is a transitive verb in this context.