insouciant vs casual

insouciant and casual both are adjectives.

Word	Noun	Adjective	Verb	Adverb
insouciant	No	Yes	No	No
casual	No	Yes	No	No

As adjectives, insouciant and casual are synonyms defined as:

Other synonyms of insouciant include nonchalant.

insouciant (adjective)	casual (adjective)
marked by blithe unconcern	hasty and without attention to detail; not thorough
	not showing effort or strain
	occurring on a temporary or irregular basis
	marked by blithe unconcern
	appropriate for ordinary or routine occasions
	occurring or appearing or singled out by chance
	natural and unstudied
	characterized by a feeling of irresponsibility
	without or seeming to be without plan or method; offhand