(glossary entry; plural = Rupes)
One of 18 different categories of lunar features recognized in the current system of IAU nomenclature. The IAU defines a Rupes as a "scarp". The term is used as prefix to the feature name.
Once again the IAU has chosen the wrong definition. Scarps are common on the Moon - the steep interior of every fresh crater is a scarp, but they have never been considered rupes! Rupes are faults, and there are only a handful on the Moon. - tychocrater Sep 2, 2007
Wikipedia (Terrestrial Fault)
A scarp is a one-sided feature with the terrain on one side being at a substantially different elevation from that on the other. This differs from a rille ("rima") or a ridge ("dorsa") where the land on either side is at the same height. - Jim Mosher
List of Lunar Faults