Transwarp threshold
From Memory Alpha, the free Star Trek reference.
The transwarp threshold is a boundary that separates warp from transwarp and is identified as the velocity of warp factor 10.
In 2372, Tom Paris crossed the transwarp threshold while attempting to devise a means to help his ship, the USS Voyager, hasten its journey back to the Alpha Quadrant. (VOY: "Threshold")
