a timepiece or timing device with a
special mechanism for ensuring and adjusting its accuracy, for
use in determining
longitude (the distance east or
west on the Earth's surface, measured in degrees from a certain meridian, a
line from the
North to the
South Pole) at
sea or for any
purpose where very exact measurement of
time is required.
—Ability Congress Approved Glossary, —9th ACC Volume 3 Approved Glossary