1. 
   Hack watch
   A hack watch is a watch used on a ship`s deck when taking astronomical sights for navigational purposes. Accuracy can be checked by comparing daily with the ship`s marine chronometer. The use of a hack watch makes it easier to take sights, as the chronometer is normally in a fixed position in a shi...
   Found op http://en.wikipedia.org/wiki/Hack_watch
   
   
2. 
   Hack-Watch
   (often abbreviated to ‘hack`)   A watch with a small lever under the dial which thrusts a wire hook between the teeth of the escape-wheel or fourth wheel, thus stopping the movement.   This device became popular soon after 1800 (concurrently with the increasing use of the seconds dial), ...
   Found op http://www.timtemplewatches.com/information_watch_dictionary1.html
   
   

Tip: double click on a word to show its meaning.