oldtimer vs expert

oldtimer and expert both are nouns.

Word	Noun	Adjective	Verb	Adverb
oldtimer	Yes	No	No	No
expert	Yes	Yes	No	No

As nouns, expert is a hypernym of oldtimer; that is, expert is a word with a broader meaning than oldtimer:

oldtimer: an experienced person who has been through many battles; someone who has given long service
expert: a person with special knowledge or ability who performs skillfully

oldtimer (noun)	expert (noun)
an elderly man	a person with special knowledge or ability who performs skillfully
an experienced person who has been through many battles; someone who has given long service

oldtimer (adjective)	expert (adjective)
	having or showing knowledge and skill and aptitude
	of or relating to or requiring special knowledge to be understood