planetary gear

English Thesaurus

1. an outer gear that revolves about a central sun gear of an epicyclic train (noun.artifact)

hypernym	:	cogwheel, gear, gear wheel, geared wheel,
definition	:	a toothed wheel that engages another toothed mechanism in order to change the speed or direction of transmitted motion (noun.artifact)

part meronym	:	epicyclic gear train, epicyclic train,
definition	:	a system of epicyclic gears in which at least one wheel axis itself revolves about another fixed axis (noun.artifact)