old-timer vs warhorse

old-timer and warhorse both are nouns.

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

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

old-timer and warhorse: 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, oldtimer, stager, veteran.

old-timer (noun)	warhorse (noun)
an elderly man	horse used in war
an experienced person who has been through many battles; someone who has given long service	a work of art (composition or drama) that is part of the standard repertory but has become hackneyed from much repetition
	an experienced person who has been through many battles; someone who has given long service