/ ˈmetrənəʊm; NAmE -noʊm/ noun
a device that makes a regular sound like a clock and is used by musicians to help them keep the correct rhythm when playing a piece of music
► met·ro·nom·ic / ˌmetrəˈnɒmɪk; NAmE -ˈnɑːm-/ adjective :
His financial problems hit the headlines with almost metronomic regularity.
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WORD ORIGIN
early 19th cent.: from Greek metron measure + nomos law.