-nt adjective
Etymology: French, from Old French, from present participle of nonchaloir to disregard, make light of, from non- non- (I) + chaloir to be of interest to, concern, from Latin calēre to be warm — more at lee
: marked by or reflecting an attitude of nonchalance : having a manner or air of jaunty unconcern or indifference : unruffled , imperturbable
a hastily assumed air of nonchalant confidence — J.B.Priestley
drove the car with nonchalant abandon
nonchalant amid the booming of guns
Synonyms: see cool