old-timer vs oldtimer

old-timer and oldtimer both are nouns.

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

As nouns, old-timer and oldtimer are synonyms defined as:

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

As nouns, old-timer and oldtimer are synonyms defined as:

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

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

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