Rotating Engine Disc That Smoothes Out Speed
Puzzle 15 of Winter Wonderland Piece of Cake Pack
Question is: Rotating Engine Disc That Smoothes Out Speed
and the answer is: FLYWHEEL
Word Meaning:
FLYWHEEL — (mechanical engineering) A rotating mass used to maintain the speed of a machine within certain limits while the machine receives or releases energy at a varying rate, or as a form of energy storage.
Definitions from Wiktionary.