Answer: chronometer

AnswerCrossword Clue
CHRONOMETERTimekeeping instrument
CHRONOMETERWatch, say
CHRONOMETERShip's clock
chronometeran instrument for measuring time
chronometera timepiece with a special mechanism for ensuring and adjusting its accuracy, usually for use in determining longitude at sea.
chronometerAn instrument for measuring time, esp. one designed to keep accurate time in spite of motion or variations in temperature, humidity, and air pressure. Chronometers were first developed for marine navigation, being used in conjunction with astronomical observation to determine longitude