E

Ebauche - a base watch movement. A set of loose parts made up of the main plate, the bridges, the train, the winding and setting mechanism and the regulator.  It does not include the timing system, the escapement or the mainspring.

Ecomax - a low-battery warning system.  The second hand is caused to jump at 2, 3 or 4 second intervals before the battery dies.  This gives you time to replace the battery while the watch is still keeping time.

Engine Turning - decorative engraving

Equation of Time - the difference between clock time and time defined by the position of the sun.

Equator - This line of latitude located half way between the North and South pole.  
It is 24,901.55 miles (40,075.16 kilometers) long. The equator divides the planet into the Northern and Southern Hemispheres. 

Escapement - The most important part of the watch.  Converts the energy of the mainspring into equal units of time.  The escapement allows the power stored in the mainspring to be released in a controlled manner.  The regularity is controlled by the balance and it's spring.  The escapement controls the rotation of the wheels and thus the motion of the hands. It is fitted at the end of the gear-train and is designed to interrupt the movement of the wheels at regular intervals.

Escape Wheel - in a lever escapement this is the last gear in the gear train. 

ETA - leading manufacturer in Switzerland for movements used in many Swiss watch brands.

Etablisseur - French term for a factory that assembles watches without producing the components.