insouciant

[Bailey]

in·sou·ci·ant (n-ss-nt, s-syä)
adj.
Marked by blithe unconcern; nonchalant.


[French : in-, not (from Old French; see in-1) + souciant, present participle of soucier, to trouble (from Old French, from Vulgar Latin *sollictre, alteration of Latin sollicitre, to vex; see solicit).]



in·souci·ant·ly adv.

The American Heritage® Dictionary of the English Language, Fourth Edition copyright ©2000 by Houghton Mifflin Company. Updated in 2003. Published by Houghton Mifflin Company. All rights reserved.

mark I'd-explain-but-I really-don't-care-to Bailey

[Perry]

A word rife with that certain je ne sai qua.