From Macross Compendium
A type of Overtechnology similar to nuclear fusion. Unlike nuclear fusion however, this energy reaction became an excellent power source of extreme efficiency, since the fuel does not necessarily have to be nuclear material and is also easily maintained in plasma state with the use of super dimension spatial theory.
The intentionally vague "reaction" concept was used as an euphemism to avoid mentioning the words "nuclear weaponry" on-screen. According to Kawamori Shoji, the use of nuclear weaponry by the "good guys" was considered taboo by Japanese television stations. (It was not considered "taboo" to use "thermonuclear" in the context of power systems and engines.) When it was noted to him that pair-annihilation reaction ("currently" being used in the Macross universe) is even more destructive than thermonuclear reaction, Kawamori observed that since pair-annihilation weapons don't exist (yet), there are no protesters.