—n. 1. (not in technical use) a gear tooth, formerly esp. 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.
—v.i. (of an electric motor) to move jerkily.
—v.t. 1. to roll or hammer (an ingot) into a bloom or slab.
2. slip a cog, to make a blunder; err: One of the clerks must have slipped a cog.