Lohrmann is a small lunar crater that is located to the west of the Oceanus Procellarum, near the western limb. It lies to the north of the dark-floored walled plain Grimaldi, and just to the south of the crater Hevelius. This crater is nearly circular, although it does not appear so from the Earth due to foreshortening. It has a narrow inner wall at the north end and a somewhat eroded edge. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.
