What is the ninth dimension?

It's basically meaningless technobabble.

There are some theories that say the Universe has additional dimensions beyond the obvious three, and time is sometimes considered as the "fourth dimension" (again, in addition to the three spatial once that we're familiar with). However, beyond that, there's no real meaning that can be ascribed to any of these dimensions; we're not even sure they "really" exist (the math in certain physical theories works out nicely if they do, but the universe as a whole doesn't really care about how nicely our mathematics works).