Warbird was a type of warship classification, primarily used within the Romulan Star Empire. The classification was one of nomenclature and in fact comprised a number of ships with widely varying combat roles.
The primary technological distinction was that rather than using a matter-antimatter reaction to generate power for its warp drive, a warbird instead captured radiation produced by dropping mass into an artificial quantum singularity. This allowed for much more variation in power output than a matter-antimatter reactor, but the downside was that if the containment systems were disrupted the ship would be crushed in seconds.
Known classes of warbirds