nonchalant
adjective
1. marked by blithe unconcern
- drove his car with nonchalant abandon
- was polite in a teasing nonchalant manner
Similar word(s): unconcerned, casual, insouciant
Sentences with nonchalant as an adjective:
- We handled the whole frenetic situation with a nonchalant attitude.
- He is far too nonchalant about such a serious matter.