How do u rename on the hour? what does on the hour mean? ? plz guys i really would appreciate it i will give u 43 points if u answer

For example, if someone says "5, on the hour", it means at 5:00

On the hour means that it's exactly an hour. An example would be 5:00 on the hour. Therefore, it would be exactly 5:00. Not 5:01 or 4:59. 

You can rephrase this by saying:
"On the Dot"
"Exactly __ o clock"

Idon’t even know the answer hehehehe