flywheel

• POS: Noun
• HYPHEN: fly=wheel

CIDE DICTIONARY

flywheel, n. 

 A heavy wheel or disk which stores kinetic energy by rotating on a shaft, and by its momentum smoothes the operation of a reciprocating engine by reducing fluctuations of speed. It is used in certain types of machinery, such as automobiles.  [WordNet 1.5]
" Flywheels rotating at high speed have also been proposed as a means to store kinetic energy for use as a low-polluting source of energy in vehicles."  [PJC]

OXFORD DICTIONARY

flywheel, n. a heavy wheel on a revolving shaft used to regulate machinery or accumulate power.

ROGET THESAURUS

flywheel

Rotation

N rotation, revolution, spinning, gyration, turning about an axis, turning aound an axis, circulation, roll, circumrotation, circumvolution, circumgyration, volutation, circination, turbination, pirouette, convolution, verticity, whir, whirl, eddy, vortex, whirlpool, gurge, countercurrent, Maelstrom, Charybdis, Ixion, cyclone, tornado, whirlwind, dust devil, spin-out, axis, axis of rotation, swivel, pivot, pivot point, axle, spindle, pin, hinge, pole, arbor, bobbin, mandrel, axle shaft, gymbal, hub, hub of rotation, helix, helical motion, angular momentum, angular velocity, revolutions per minute, RPM, centrifugal force, surge, vertigo, dizzy round, coriolus force, carousel, merry-go-round, Ferris wheel, top, dreidel, teetotum, gyroscope, turntable, lazy suzan, screw, whirligig, rollingstone, water wheel, windmill, wheel, pulley wheel, roulette wheel, potter's wheel, pinwheel, gear, roller, flywheel, jack, caster, centrifuge, ultracentrifuge, bench centrifuge, refrigerated centrifuge, gas centrifuge, microfuge, drill, augur, oil rig, wagon wheel, wheel, tire, tyre, trochilics, whirling dervish, rotating, rotary, rotary, circumrotatory, trochilic, vertiginous, gyratory, vortical, vorticose, head over heels, round and round, like a horse in a mill.