The Collaborative International Dictionary of English v.0.48:
Steadfastly \Stead"fast*ly\, adv. In a steadfast manner; firmly. [1913 Webster] Steadfastly believe that whatever God has revealed is infallibly true. --Wake. [1913 Webster]WordNet (r) 3.0 (2006):
steadfastly adv 1: with resolute determination; "we firmly believed it"; "you must stand firm" [syn: firm, firmly, steadfastly, unwaveringly]