sharpshooter vs marksman

sharpshooter and marksman both are nouns.

Word	Noun	Adjective	Verb	Adverb
sharpshooter	Yes	No	No	No
marksman	Yes	No	No	No

As nouns, sharpshooter and marksman are synonyms defined as:

Other synonyms of sharpshooter include crack shot.

sharpshooter (noun)	marksman (noun)
a fast schooner once used by New England fisherman for illegal fishing in Canadian waters	someone skilled in shooting
someone skilled in shooting
an athlete noted for accurate aim