o’clock (?-kl?k?)adv.1. Of or according to the clock: three o’clock.2. According to an imaginary clock dial with the observer at the center and 12 o’clock considered as straight ahead in horizontal position or straight up in vertical position. Used to indicate relative position: enemy planes at 10 o’clock.[Short for of the clock.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.o’clock (??kl?k) adv1. used after a number from one to twelve to indicate the hour of the day or night2. (Navigation) used after a number to indicate direction or position relative to the observer, twelve o’clock being directly ahead or overhead and other positions being obtained by comparisons with a clock face[C18: abbreviation for of the clock]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014o’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.