bilingualism

from WordNet (r) 3.0 (2006)

bilingualism
    n 1: the ability to speak two languages colloquially

from The Collaborative International Dictionary of English v.0.48

Bilingualism \Bi*lin"gual*ism\, n.
   Quality of being bilingual.
   [1913 Webster]

         The bilingualism of King's English.      --Earle.
   [1913 Webster]