1. 无动于衷的;漠不关心的
If you describe someone as nonchalant, you mean that they appear not to worry or care about things and that they seem very calm.

1. marked by blithe unconcern

e.g. an ability to interest casual students
showed a casual disregard for cold weather
an utterly insouciant financial policy
an elegantly insouciant manner
drove his car with nonchalant abandon
was polite in a teasing nonchalant manner

Synonym: casualinsouciant