RhymeZone: mascon definitions

Definitions of mascon:

noun: A region within a solid astronomical body that is of higher density than the surrounding material.
noun: A lunar mare that has a greater density of rock than the surrounding area.
noun: (astronomy) mass concentration
noun: (obsolete) Synonym of Mâcon.
noun: (obsolete) Synonym of Macon.

(Definitions from Wiktionary)