Source : Webster's Revised Unabridged Dictionary (1913)

Cavalierly \Cav`a*lier"ly\, adv.
   In a supercilious, disdainful, or haughty manner; arrogantly.
   --Junius.

Source : WordNet®

cavalierly
     adv : in a proud and domineering manner; "he treated his staff
           cavalierly" [syn: {disdainfully}]