Definition of
O'clock
- (adv, all) according to the clock
via WordNet, Princeton University
Origin of the word O'clock
- c.1720, abbreviation of of the clock, from M.E. of the clokke (1389). Attested from 1904 in ref. to direction (by shooters, fighter pilots, etc.).
via Online Etymology Dictionary, ©2001 Douglas Harper
People who say O'clock

Seth_McCann RT @ThaKingXerxes: It's 1 o'clock and I graduate tomorrow night...anddddd I'm not even tired. The F?

DanielLockyer @Triplenox I went to bed at 2 o clock this morning because I don't have school today :D

FrankieBagshaw 2 hour multiple choice exam to look forward to at 9 o'clock #luckygirl #not

miranda334 Seriously?! I honestly don't think I can go to bed before 12 o'clock anymore... I somehow always manage to stay awake till the early AM..
via Twitter
