Source : Webster's Revised Unabridged Dictionary (1913)

Blithely \Blithe"ly\, adv.
   In a blithe manner.

Source : WordNet®

blithely
     adv : in a joyous manner; "they shouted happily" [syn: {happily},
           {merrily}, {mirthfully}, {gayly}, {jubilantly}, {with
           happiness}] [ant: {unhappily}]