The Collaborative International Dictionary of English v.0.48:
Blissful \Bliss"ful\, a. Full of, characterized by, or causing, joy and felicity; happy in the highest degree. "Blissful solitude." --Milton. -- Bliss"ful*ly, adv. -- Bliss"ful*ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
blissfully adv 1: in a blissful manner; "he was blissfully unaware of the danger"