A star desert is a region of space which has zero space density. There is no change in gravimetric readings inside the void.
There is a star desert nine hundred light years away from Earth in Quadrant 904. In 2267, this region was crossed by USS Enterprise to reach Beta VI to deliver supplies. It would have taken eight days to cross the region at warp 3. The planet Gothos was created inside this void by Trelane. (TOS: "The Squire of Gothos")