(glossary entry; plural = Planitiae)
One of 18 different categories of lunar features recognized in the current system of IAU nomenclature. The IAU defines a planitia as a "low plain". The term is used as prefix to the feature name.
The plural form is a bit superfluous in the present context, since there is only one "planitia" on the Moon: Planitia Descensus.
- Jim Mosher