Epyon System: a system installed in Epyon almost identical to the Zero system

Gundam: a mobile suit made from Gundaminum alloy

Gundanium:
an almost impenetrable substance developed in space; used to create Gundams

Lagrange Points (L1,L2,L3,L4,L5): points at which the colonies orbit.

Operation Meteor:
a military operation planned and executed by five scientists, each on separate colonies. The goal was to send the five Gundams which they had individually engineered to Earth. where they would battle the newly emerging OZ

Maganac:
A group of mercenary Arabs with MS loyal to Quatre Winner. Not much is revealed about their origin in the anime,but the manga reveals that they are all genetically engineered, as Quatre believes he is as well.

mecha:
the term to describe a humanoid robot used for battling, such as the MS. Other examples are Robotech, Escaflowne and Evangelion(which is a little different, but basically mecha)

Mobile Dolls:
Mecha with an AI system in the cockpit instead of a human pilot

MS: Abbreviation for Mobile Suit

Zero System:
The system that was first installed in Wing Zero. It connects the pilot's brainwaves more directly to the MS's systems, increasing the performance of the Suit. Sometimes it seems to control the pilot, usually causing increased agression and temporary insanity. The system was only mastered by Heero Yuy, Quatre Winner and Dorothy Catalonia.