caterpillar track

Wiktionary

1. n. A continuous track in the form of steel or rubber belt fitted instead of wheels to crawlers, bulldozers, tanks and similar off-road vehicles.

GNU Webster's 1913

1. n. an endless belt looped over several wheels, used in pairs in place of wheels to propel vehicles, such as tractors or military tanks, over rough ground.

WordNet 3.0

1. n. an endless metal belt on which tracked vehicles move over the ground