Source : Webster's Revised Unabridged Dictionary (1913)

Nonchalantly \Non"cha*lant`ly\, adv.
   In a nonchalant, indifferent, or careless manner; coolly.

Source : WordNet®

nonchalantly
     adv 1: in a composed and unconcerned manner; "without more ado
            Barker borrowed a knife from his brigade Major and
            honed it on a carborundum stone as coolly as a
            butcher" [syn: {coolly}, {nervelessly}]
     2: in an unconcerned manner; "glanced casually at the
        headlines" [syn: {casually}]