o’clock (??kl?k) adv. 1. of, by, or according to the clock (used in specifying the hour of the day): 11 o’clock. 2. according to a method for indicating a position in space relative to the numbers on a clock’s face, with 12 o’clock directly ahead in horizontal position or straight up in vertical position. [1710?20] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.