The Collaborative International Dictionary of English v.0.48:
Merrily \Mer"ri*ly\, adv. [From Merry.] In a merry manner; with mirth; with gayety and laughter; jovially. See Mirth, and Merry. [1913 Webster] Merrily sing, and sport, and play. --Granville. [1913 Webster]WordNet (r) 3.0 (2006):
merrily adv 1: in a joyous manner; "they shouted happily" [syn: happily, merrily, mirthfully, gayly, blithely, jubilantly] [ant: unhappily]