oldtimer vs old geezer

oldtimer and old geezer both are nouns.

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

As nouns, oldtimer and old geezer are synonyms defined as:

Other synonyms of oldtimer include antique, gaffer, old-timer.

oldtimer (noun)	old geezer (noun)
an elderly man	an elderly man
an experienced person who has been through many battles; someone who has given long service