The Collaborative International Dictionary of English v.0.48:

Rebellious \Re*bel"lious\ (r[-e]*b[e^]l"y[u^]s), a.
   Engaged in rebellion; disposed to rebel; of the nature of
   rebels or of rebellion; resisting government or lawful
   authority by force. "Thy rebellious crew." "Proud rebellious
   arms." --Milton. -- Re*bel"lious*ly, adv. --
   Re*bel"lious*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rebelliously
    adv 1: in a rebellious manner; "he rejected her words
           rebelliously" [syn: rebelliously, contumaciously,
           defiantly]