Source : Webster's Revised Unabridged Dictionary (1913)

Insouciant \In`sou`ciant"\, a. [F.]
   Careless; heedless; indifferent; unconcerned. --J. S. Mill.

Source : WordNet®

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}]