Gramps and Oldtimer

Gramps noun - The father of your father or mother.

Oldtimer and gramps are semantically related In some cases you can replace term "Oldtimer" with "Gramps", this nouns are similar.

Oldtimer noun - An experienced person who has been through many battles; someone who has given long service.

Gramps and oldtimer are semantically related in elderly person topic. Sometimes you can use "Gramps" instead a noun "Oldtimer".