The Collaborative International Dictionary of English v.0.48:
Stoutly \Stout"ly\, adv. In a stout manner; lustily; boldly; obstinately; as, he stoutly defended himself. [1913 Webster]WordNet (r) 3.0 (2006):
stoutly adv 1: in a resolute manner; "he was stoutly replying to his critics"