reckless vs rash

reckless is not a noun while rash is a noun.

Word	Noun	Adjective	Verb	Adverb
reckless	No	Yes	No	No
rash	Yes	Yes	No	No

As adjectives, reckless and rash are synonyms defined as:

reckless and rash: marked by defiant disregard for danger or consequences

Other synonyms of reckless include foolhardy, heady.

reckless (noun)	rash (noun)
	a series of unexpected and unpleasant occurrences
	any red eruption of the skin

reckless (adjective)	rash (adjective)
marked by defiant disregard for danger or consequences	marked by defiant disregard for danger or consequences
characterized by careless unconcern	imprudently incurring risk