If I were diagramming it, I think I’d still label “accidentally” as an adverb, but would note that the corresponding verb has been omitted. It’s the written eq

If I were diagramming it, I think I’d still label “accidentally” as an adverb, but would note that the corresponding verb has been omitted. It’s the written equivalent of hearing “Oh my, there’s a gigantic <RADIO STATIC> blocking the road.” The unknown word blocked by the radio static is still the noun, we just don’t know what it is.