What is O'clock?
1.
a) The hour on a 12 hour clock.
b) The position of something to you, 12 O'clock being straight ahead, six being behind, 3 O'Clock 90 degrees clockwise and 9 being 90 degrees anti-clockwise.
The time is 9 O'clock (well, 21:29) and having found no good tv, I turned on the PC and defined this word and a half.
Charlie at five o'clock sir!
See
2.
The time at which people have sex in an office.
Secretary: "It's time!"
Principle: "Thank heavens its O'clock!"