oldtimer vs old man

oldtimer and old man both are nouns.

Word	Noun	Adjective	Verb	Adverb
oldtimer	Yes	No	No	No
old man	Yes	No	No	No

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

Other hypernyms of oldtimer include graybeard, greybeard, Methuselah.

oldtimer (noun)	old man (noun)
an elderly man	an informal term for your father
an experienced person who has been through many battles; someone who has given long service	a man who is very old
	a familiar term of address for a man
	(slang) boss
	aromatic herb of temperate Eurasia and North Africa having a bitter taste used in making the liqueur absinthe