Battlecruiser is an unofficial classification of warship (not ratified by the Interstellar Standard Warship Classification System) referring primarily to a Reunification Navy programme to develop the smallest-possible ship capable of fighting in the battleline. As such, they lack the multi-role capabilities of conventional lineships, but in exchange are smaller and cheaper while still possessing heavy firepower.
Since the RN programme, various other navies have also developed battlecruisers. Often these were referred to by their own proprietary terms, but in the name of sensibleness this article will consider them to be battlecruisers since this fits closely.
Extant Classes:
Audacious-class Battlecruiser (Reunification Navy)
Castle-class Battlecruiser (Reunification Navy)
Constellation-class Battlecruiser (Reunification Navy)
YBC-43 Space Supremacy Ship (Yundari Navy)
Invincible-class Battlecruiser (Celestian Navy)
Impenetrable-class Battlecruiser (Celestian Navy)