The Collaborative International Dictionary of English v.0.48:
Illegally \Il*le"gal*ly\, adv. In a illegal manner; unlawfully. [1913 Webster]WordNet (r) 3.0 (2006):
illegally adv 1: in an illegal manner; "they dumped the waste illegally" [syn: illegally, illicitly, lawlessly] [ant: lawfully, legitimately, licitly]