flywheel

UK: /ˈflaɪˌwiːl/ US: /ˈflaɪˌhwil, -ˌwil/ ,(flī′hwēl′, -wēl′)

WordReference Random House Learner's Dictionary of American English © 2026

fly•wheel /ˈflaɪˌhwil, -ˌwil/   n. [countable]

1. Mechanical Engineering a heavy wheel that regulates the speed of the shaft and all connected machinery.

WordReference Random House Unabridged Dictionary of American English © 2026

fly•wheel  (flī′hwēl′, -wēl′), n. [Mach.]

1. Mechanical Engineering a heavy disk or wheel rotating on a shaft so that its momentum gives almost uniform rotational speed to the shaft and to all connected machinery.

• fly¹ + wheel 1775–85

Collins Concise English Dictionary © HarperCollins Publishers::

flywheel / ˈflaɪˌwiːl/ noun

1. a heavy wheel that stores kinetic energy and smooths the operation of a reciprocating engine by maintaining a constant speed of rotation over the whole cycle