Many a scholar have defined it. However, I would prefer the following definition:
“It is any authentic recitation of the Book that the Prophet Muhammad  said was revealed to him by Allah (God) through the Archangel Jibreel (Gabriel).”

Explanation:

1. The word Quran ( قران or قرءان) is from the root word qaraa (قرأ) which means to recite. So it is a recitation.

2. It is not just any oral recitation. It is a recitation of a written book.

3. Of all the written books that are recited, this is the one that Prophet Muhammad said was revealed to him.

5. The recitation must be famous. Ten of these recitations have survived.