From The Collaborative International Dictionary of English v.0.48 [gcide]:
Caterpillar track \Cat"er*pil`lar track\, 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.
[PJC]
From WordNet (r) 3.0 (2006) [wn]:
caterpillar track
n 1: an endless metal belt on which tracked vehicles move over
the ground [syn: track, caterpillar track, {caterpillar
tread}]