From Longman Dictionary of Contemporary Englisholdsterold‧ster /ˈəʊldstə $ ˈoʊldstər/ noun [countable] informal OLD/NOT YOUNGan old person
Examples from the Corpus
oldster• But the oldster in me keeps worrying about people getting hurt.• The oldsters have had their quota.• Every long table is filled with oldsters in their golden years costumes-juvenile ensembles of short pants, shirts, and sneakers. 