old-timer vs old man

old-timer and old man both are nouns.

Word	Noun	Adjective	Verb	Adverb
old-timer	Yes	No	No	No
old man	Yes	No	No	No

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

Other hypernyms of old-timer include graybeard, greybeard, Methuselah.

old-timer (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