marathon runner vs road runner

marathon runner and road runner both are nouns.

Word	Noun	Adjective	Verb	Adverb
marathon runner	Yes	No	No	No
road runner	Yes	No	No	No

As nouns, marathon runner and road runner are synonyms defined as:

marathon runner and road runner: someone who participates in long-distance races (especially in marathons)

Other synonyms of marathon runner include long-distance runner, marathoner.

marathon runner (noun)	road runner (noun)
someone who participates in long-distance races (especially in marathons)	someone who participates in long-distance races (especially in marathons)