RhymeZone: reg definitions

Definitions of reg:

noun: (Internet slang) A regular.
noun: (informal) A regulation.
noun: registrar
noun: registration
noun: registry
noun: (geography) A hard surface of rock fragments set in a sandy matrix, found in some hot deserts; regolith, stony desert.
noun: A diminutive of the male given name Reginald

(Definitions from Wiktionary)