The Collaborative International Dictionary of English v.0.48:

Adriatic \A`dri*at"ic\, a. [L. Adriaticus, Hadriaticus, fr.
   Adria or Hadria, a town of the Veneti.]
   Of or pertaining to a sea so named, the northwestern part of
   which is known as the Gulf of Venice.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Adriatic
    n 1: an arm of the Mediterranean between Slovenia and Croatia
         and Montenegro and Albania on the east and Italy on the
         west [syn: Adriatic, Adriatic Sea]