Ctesibius (Moon)

Named after Ctesibius - Egyptian physicist (unkn-c. 100 B.C.).

Ctesibius is a small lunar impact crater that is located near the equator, on the far side. It lies. The outer wall is wide and sharp-edged, with little erosion. A low ridge is attached to the southern rim, and curves to the south-southeast. (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.