noun
or differential gearing
1. : an arrangement of gears forming an epicyclic train for connecting two shafts or axles in the same line, dividing the driving force equally between them, and permitting one shaft to revolve faster than the other when required (as by the driving wheels of an automobile that is moving in a curve), the speed of the main driving member being always equal to the algebraic mean of the speeds of the two shafts
2. : planet differential