insouciant 
September 3, 2006 | 15:55

insouciant - Definitions from Dictionary.com (etymology):

insouciant (in-SOO-see-uhnt) adjective

Marked by blithe unconcern; nonchalant.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.