cog /kɒɡ $ kɑːɡ/ BrE AmE noun [countable]
[ Date: 1200-1300 ; Origin: From a Scandinavian language ]
1 . a wheel with small bits sticking out around the edge that fit together with the bits of another wheel as they turn in a machine
2 . one of the small bits that stick out on a cog
3 . a cog in the machine/wheel someone who only has a small unimportant job in a large organization