The Collaborative International Dictionary of English v.0.48:
Blithely \Blithe"ly\, adv. In a blithe manner. [1913 Webster]WordNet (r) 3.0 (2006):
blithely adv 1: in a joyous manner; "they shouted happily" [syn: happily, merrily, mirthfully, gayly, blithely, jubilantly] [ant: unhappily]