A globular cluster was a kind of stellar cluster. Starship navigation within a globular cluster could be difficult due to gravimetric interference.
In 2369, the USS Enterprise-D charted an unusually dense globular cluster, the Amargosa Diaspora. (TNG: "Schisms")
In 2401, globular cluster was listed as one of the results in Raffaela Musiker's search for the "red lady". (PIC: "The Next Generation")