ball bearing
From Longman Dictionary of Contemporary EnglishRelated topics: Technology, Mechanicalball bearingˌball ˈbearing noun [countable] 1 Tan arrangement of small metal balls that move in a ring, to make a part inside a machine turn more easily2 Tone of these metal ballsExamples from the Corpusball bearing• In the first system the rotation of the mouse's wheels or ball bearing are transferred to rollers.