An example of a Super Weapon, the Spiridus
Superweapon is a term colloquially used to define any aircraft or ground installaition whose combat capabilities are far beyond those of normal warfare vehicles and are typically designed to inspire fear of their power rather than as a viable weapon, as most are so expensive as to be nearly impractical. Examples of this include vehicles/installations armed with railguns, burst missiles and laser weaponry. Usually, a super weapon is far bigger than any other installation/vehicle.
The greatest example of Super Weapons are airship, which have appeared in nearly every Ace Combat title ever since Air Combat, with a notable aversion being in The Unsung War, where the local "airship" is an anti-asteroid space plane, the Arkbird.
Note that super aircraft are sometimes confused with super weapons due to their combat abilities. While some of them have superweapon traits (such as the Strigon's CFA-44 Nosferatu, which has a UAV control system & ADMM pods), those traits are only seen in certain superaircraft flyable both by the player and the enemy (see the previous example.)