The Collaborative International Dictionary of English v.0.48:
Bitterly \Bit"ter*ly\, adv. In a bitter manner. [1913 Webster]WordNet (r) 3.0 (2006):
bitterly adv 1: with bitterness, in a resentful manner; "she complained bitterly" 2: indicating something hard to accept; "he was bitterly disappointed" 3: extremely and sharply; "it was bitterly cold"; "bitter cold" [syn: piercingly, bitterly, bitingly, bitter]