Historically, grammarians have described a verbal noun or gerundial noun as a verb form that functions as a noun. An example of a verbal noun in English is 'sacking' as in the sentence "The sacking of the city was an epochal event" (wherein sacking is a gerund form of the verb sack).
A verbal noun, as a type of nonfinite verb form, is a term that some grammarians still use when referring to gerunds, gerundives, supines, and nominal forms of infinitives. In English however, verbal noun has most frequently been treated as a synonym for gerund.
