The Collaborative International Dictionary of English v.0.48:

Accadian \Ac*ca"di*an\, a. [From the city Accad. See Gen. x.
   10.]
   Pertaining to a race supposed to have lived in Babylonia
   before the Assyrian conquest.
   [1913 Webster] -- Ac*ca"di*an, n., Ac"cad, n. --Sayce.
   [1913 Webster]