race runner vs racerunner

race runner and racerunner both are nouns.

Word	Noun	Adjective	Verb	Adverb
race runner	Yes	No	No	No
racerunner	Yes	No	No	No

As nouns, race runner and racerunner are synonyms defined as:

race runner and racerunner: very swift lizard of eastern and central United States

Other synonyms of race runner include Cnemidophorus sexlineatus, six-lined racerunner.

race runner (noun)	racerunner (noun)
very swift lizard of eastern and central United States	very swift lizard of eastern and central United States