runabout vs roadster

runabout and roadster both are nouns.

Word	Noun	Adjective	Verb	Adverb
runabout	Yes	No	No	No
roadster	Yes	No	No	No

As nouns, runabout and roadster are synonyms defined as:

runabout and roadster: an open automobile having a front seat and a rumble seat

Other synonyms of runabout include two-seater.

runabout (noun)	roadster (noun)
an open automobile having a front seat and a rumble seat	a small lightweight carriage; drawn by a single horse
	an open automobile having a front seat and a rumble seat