• synonyms


[kog, kawg]
See more synonyms on Thesaurus.com
  1. (not in technical use) a gear tooth, formerly especially one of hardwood or metal, fitted into a slot in a gearwheel of less durable material.
  2. a cogwheel.
  3. a person who plays a minor part in a large organization, activity, etc.: He's just a small cog in the financial department.
verb (used without object), cogged, cog·ging.
  1. (of an electric motor) to move jerkily.
verb (used with object), cogged, cog·ging.
  1. to roll or hammer (an ingot) into a bloom or slab.
  1. slip a cog, to make a blunder; err: One of the clerks must have slipped a cog.

Origin of cog1

1200–50; Middle English cogge, probably < Scandinavian; compare Swedish, Norwegian kugg cog
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for slip a cog


  1. any of the teeth or projections on the rim of a gearwheel or sprocket
  2. a gearwheel, esp a small one
  3. a person or thing playing a small part in a large organization or process
verb cogs, cogging or cogged
  1. (tr) metallurgy to roll (cast-steel ingots) to convert them into blooms

Word Origin

C13: of Scandinavian origin; compare Danish kogge, Swedish kugge, Norwegian kug


verb cogs, cogging or cogged
  1. slang to cheat (in a game, esp dice), as by loading a dice

Word Origin

C16: originally a dice-playing term, of unknown origin


  1. a tenon that projects from the end of a timber beam for fitting into a mortise
verb cogs, cogging or cogged
  1. (tr) to join (pieces of wood) with cogs

Word Origin

C19: of uncertain origin
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for slip a cog



c.1300, "cog wheel;" late 14c., "tooth on a wheel," probably a borrowing from a Scandinavian language (cf. Norwegian kugg "cog") and cognate with Middle High German kugel "ball."

Online Etymology Dictionary, © 2010 Douglas Harper

Idioms and Phrases with slip a cog

slip a cog

Also, slip a gear or one's gears. Lose one's ability to reason soundly or make correct judgments, as in She must have slipped a cog or she would never have gone out barefoot in December, or What's the matter with him? Has he slipped his gears? These slangy usages allude to a mechanical failure owing to the cog of a gear or a gear failing to mesh. The first dates from about 1930, the variant from the 1960s.


In addition to the idiom beginning with cog

also see:

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.