insouciant
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A search on Google News for "insouciant Ocean's Thirteen" produced these results:
"Clooney, Pitt, Damon: as insouciant as ever, tossing off the repartee with an ease that borders on sedation." - Willamette Week
"…Steven Soderbergh… recaptures the insouciant rat-pack spirit that made his initial remake of Ocean’s Eleven so enjoyable…" - Straight.com
"..in Ocean's Thirteen, the insouciant charm wears off early, and what seemed carefree about the earlier films comes to seem careless…" - Seattle Weekly