Bottom of the hour American phrase
30 minutes after an exact hour (such as 1:30, 4:30, etc.).
I called him at five o'clock, and he told me to call back at the bottom of the hour because he was driving.
It's four o'clock now, and you have to finish this test at the bottom of the hour.
This term refers to the moment when the long hand's position is pointing toward the number 6, which is exactly midway between the previous and next hour.
Someone who is totally bad at doing something.
Mary really can't sing for toffee.