The Collaborative International Dictionary of English v.0.48:
Bilingual \Bi*lin"gual\, a. [L. bilinguis; bis twice + lingua tongue, language.] Containing, or consisting of, two languages; expressed in two languages; as, a bilingual inscription; a bilingual dictionary. -- Bi*lin"gual*ly, adv. [1913 Webster]WordNet (r) 3.0 (2006):
bilingually adv 1: in a bilingual manner; "she grew up bilingually"