Definition from Wiktionary, the free dictionary
Alternative forms 
- ageing (Commonwealth English)
- Present participle of age.
aging (plural agings)
- (intransitive) The process of becoming older or more mature.
- (transitive) Allowing something to become older.
- The owner asked the clerk to age some big bills that were due.
- (transitive) The deliberate act of making something (such as an antique) appear older than it is.
- (gerontology) Becoming senescent; accumulating damage to macromolecules, cells, tissues and organs with the passage of time
- (euphemistic) Elderly person. Only as a collective plural in "the aging"
the process of becoming older or more mature
the deliberate act of making something (such as an antique) appear older than it is
- Becoming elderly.
- The aging artist could no longer steadily hold the brush.
Usage notes 
- Comparative and superlative forms are rare.