Mohorovicic discontinuity – The rock between the earth’s crust and the mantle about 30 km below the surface.
Joshua Hall taught me this one, but he didn’t use it in the course of everyday conversation. (I am still waiting for a practical use.) I have no idea how you could use this term outside the realm of geology, but here is what this thing is: Mr. Mohorovicic discovered this area of the earth in early 1909, and it was promptly named after him. It is in the lithosphere of the earth, and serves as the boundary between the mesosphere and the asthenosphere under the ocean. Many Sci-Fi novels and TV shows reference this area, but I think only as an obscurity to give the author creditability in the scientific realm. You may see this written as Mohorovicic’s discontinuity, but I think that was a space somewhere in his head. Maybe between the practical and “I can use this at a party to impress people” nervous centers where obscure things are filtered and… Hey… I think that I have a discontinuity in that area too! Maybe Mr. Mohorovicic will be best known a hundred years later for the brain condition that he epitomized.