Context: The 180th meridian or antimeridian is the meridian 180 east or west of the Prime Meridian, with which it forms a great circle dividing the earth into the Western and Eastern Hemispheres. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it mostly passes through the open waters of the Pacific Ocean. However, the meridian passes through Russia and Fiji as well as Antarctica.

Question: what is the name of the meridian at 180 degrees?
Steam of consciousness below:
The relevant information to answer the above question is: The 180th meridian or antimeridian is the meridian 180 east or west of the Prime Meridian, with which it forms a great circle dividing the earth into the Western and Eastern Hemispheres.
So, the answer is The 180th meridian or antimeridian.