also: ストップウオッチ
stopwatch
A handheld timepiece used for measuring elapsed time, typically in sports or experiments.
コーチはストップウォッチで選手のタイムを計った。
The coach timed the athlete with a stopwatch.
実験ではストップウォッチを使って反応時間を測定した。
In the experiment, we measured reaction time using a stopwatch.
I timed how long it took to run using a stopwatch.
I pressed the stopwatch at the start signal.
He started the stopwatch as the signal was given.