stopwatch
US /ˈstɑːp.wɑːtʃ/
UK /ˈstɑːp.wɑːtʃ/

1.
Stoppuhr
a watch with a button that starts or stops the movement of the hands, used for measuring the time taken by an event
:
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The coach used a stopwatch to time the runners.
Der Trainer benutzte eine Stoppuhr, um die Läufer zu stoppen.
•
He clicked the stopwatch to begin the experiment.
Er drückte die Stoppuhr, um das Experiment zu beginnen.