nonchalant
adjective
UK/ˈnɒn.ʃᵊl.ᵊnt/
US/ˌnɑːn.ʃəˈlɑːnt/
Definitions of nonchalant adjective
displaying a relaxed and unconcerned demeanor, often suggesting a lack of interest or care
He answered the question with a nonchalant attitude.
Her reaction to the news was nonchalant, as if nothing had happened.
Despite the urgency of the situation, he walked away with a nonchalant air.