A bulge is a group of stars bunched together within a larger group. Galaxies often have such a bulge spanning its center, most easily seen if it is a disk galaxy. Current thought is that such a central bulge is likely to host a supermassive black hole.
The Milky Way's central bulge, the galactic bulge, is a region surrounding the galactic center, with a very high density of stars (cited as ten million stars within a parsec of the center). It is embedded in a bar.