Oldster
/ˈəʊldstər/
Definition 1 of 1
Pro Tip 1/3Colloquial Use
The word 'oldster' is informal and best suited for casual conversation or writing. 
My grandpa, the oldster, still jogs every morning!
Pro Tip 2/3Possibly Demeaning
'Oldster' can sometimes be seen as patronizing or dismissive towards elderly people. 
He didn't like being called an oldster, as he felt it was belittling.
Pro Tip 3/3Cultural Sensitivity
Be aware that in some cultures, referring to someone as an 'oldster' can be disrespectful. 
In her culture, it's better to say 'senior' rather than 'oldster.'