chronograph
A timepiece that records elapsed time with high precision, often used in sports and scientific measurements.
彼はクロノグラフを使ってラップタイムを計測した。
He measured the lap times using a chronograph.
ストップウォッチ is a simpler stopwatch, while クロノグラフ often implies a more sophisticated instrument, sometimes combined with a standard watch.
Borrowed from English 'chronograph', ultimately from Greek roots 'chronos' (time) and 'grapho' (write).