ˈ ̷ ̷ˌ ̷ ̷ noun
Etymology: fly (II) + wheel
1. : a heavy metal wheel for opposing and moderating by its inertia any fluctuation of speed in the machinery with which it revolves ; especially : one on an engine crankshaft to counteract variable torque during the stroke and carry the engine over the dead centers
2. : a wheel similar to a flywheel used for storing kinetic energy (as for motive power)