veteran vs oldtimer

veteran and oldtimer both are nouns.

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

As nouns, veteran and oldtimer are synonyms defined as:

veteran and oldtimer: an experienced person who has been through many battles; someone who has given long service

Other synonyms of veteran include old-timer, old hand, old stager, stager, warhorse.

veteran (noun)	oldtimer (noun)
an experienced person who has been through many battles; someone who has given long service	an elderly man
a person who has served in the armed forces	an experienced person who has been through many battles; someone who has given long service
a serviceman who has seen considerable active service

veteran (adjective)	oldtimer (adjective)
rendered competent through trial and experience