What is Cog?

Cog definition and meaning on Dictionary terms:
(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.
a cogwheel.
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