The "warp barrier" is a theroetical barrier that warp is limited to preset factors, which are unsurpassable.
- Although not specified, the warp barrier is most likely in reference to Warp 10. However, there are references of other barriers, most notably in the movie Star Trek: First Contact where Zefram Cochrane "breaks the warp barrier" in the Phoenix (which reached warp 1), and in the TV show Enterprise, where the warp barrier seemed to be warp 5.
After a series of formula "upgrades" by Kosinski in 2364, the USS Enterprise-D experienced a phenomenal surge of power during a warp speed experiment and was sent over 2,700,000 light years in a matter of minutes. After realizing what he had stumbled upon, by making the so-called "warp barrier" meaningless, Kosinski declared that science would need new definitions and new parameters to define warp speed. One suggestion was the Kosinski scale. It was later determined that the enormous speed was attained with the help of The Traveler and that Kosinski's formulae were bogus. (TNG: "Where No One Has Gone Before")