Tafsir of Al-Waqi'ah 56:80

(A revelation from the Lord of the worlds)

This is another description of the Qur’an; meaning, it is [something] revealed. It is described using the verbal noun (masdar) because it is revealed in parts (nujuman)—unlike all other books of Allah the Exalted—so it is as if it is, in itself, a revelation. For this reason, it is treated as one of its names, such that it is said: "It came in the Revelation (at-Tanzil) like so," and "The Revelation spoke of such."

It is also permissible that it is a predicate for an omitted subject, meaning: "It is a revelation," by way of commencing a new sentence (isti’naf). It has also been recited as tanzilan (in the accusative case), based on the implied verbal root nazzala tanzilan.