old hand vs veteran

old hand and veteran both are nouns.

Word	Noun	Adjective	Verb	Adverb
old hand	Yes	No	No	No
veteran	Yes	Yes	No	No

As nouns, old hand and veteran are synonyms defined as:

old hand and veteran: an experienced person who has been through many battles; someone who has given long service

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

old hand (noun)	veteran (noun)
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
	a person who has served in the armed forces
	a serviceman who has seen considerable active service

old hand (adjective)	veteran (adjective)
	rendered competent through trial and experience