Which term describes a verb in the -ing form that acts like a noun?

The term that describes a verb in the -ing form that functions as a noun is known as a gerund. Gerunds are created by taking a verb and adding -ing to it, allowing the verb to perform the role of a noun within a sentence. For example, in the sentence "Swimming is fun," the word "swimming" is derived from the verb "swim" and acts as the subject of the sentence, thus functioning as a noun.

In contrast to gerunds, a conjugated verb refers to a verb that has been modified to indicate tense, mood, voice, etc., without taking the -ing form. An infinitive is the base form of a verb, usually preceded by "to" (e.g., "to run"), serving entirely different grammatical functions. A past participle is a form of a verb typically used in perfect tenses or passive voice (e.g., "swum" in "I have swum"), and it does not take the -ing form either. Thus, the correct choice accurately identifies the specific grammatical function of the -ing form verb when it operates as a noun.