1. A highly accurate timekeeping device: This is the most common meaning. A chronometer is a clock or watch that is built and tested to meet specific standards of accuracy. These standards are set by organizations like the International Bureau of Weights and Measures (BIPM). Chronometers are used in situations where precise timekeeping is crucial, such as:

* Navigation: Historically, marine chronometers were essential for determining longitude at sea. They are still used in some specialized applications.

* Scientific research: Chronometers are used in various scientific experiments and observations that require precise timekeeping.

* Timekeeping in sports: Some competitions use chronometers to record precise times for athletes.

2. A timing device in general: Sometimes, "chronometer" can be used as a general term for any device that measures time, including stopwatches and timers. However, this usage is less common and often considered informal.

In summary: A chronometer is primarily a highly accurate timekeeping device meeting strict standards. It is usually reserved for situations where precision timing is paramount.