aging Syllabification: (ag·ing)Pronunciation: /ˈājiNG/ (also ageing)Translate aging | into Spanish Definition of aging noun the process of growing old:the external signs of aging [as modifier]:the aging process the process of change in the properties of a material occurring over a period, either spontaneously or through deliberate action. adjective (of a person) growing old; elderly:looking after aging relatives an aging population (of a thing) reaching the end of useful life; obsolescent:the world’s aging fleet of oil tankersaging in other Oxford dictionaries Definition of aging in the British & World English dictionary