insouciant
  (a.)漫不經心的
  In·sou·ciant a.  Careless; heedless; indifferent; unconcerned.
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  insouciant
       adj : marked by blithe unconcern; "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" [syn: casual, nonchalant]