gyrostabilizer

[jahy-ruh-stey-buh-lahy-zer] /ˌdʒaɪ rəˈsteɪ bəˌlaɪ zər/
noun
1.
a device for stabilizing a seagoing vessel by counteracting its rolling motion from side to side, consisting essentially of a rotating gyroscope weighing about 1 percent of the displacement of the vessel.
Also called gyroscopic stabilizer, stabilizer.
Origin
1920-25; gyro(scope) + stabilizer
British Dictionary definitions for gyrostabilizer

gyrostabilizer

/ˌdʒaɪrəʊˈsteɪbɪˌlaɪzə/
noun
1.
a gyroscopic device used to stabilize the rolling motion of a ship