The Collaborative International Dictionary of English v.0.48:

Adjacent \Ad*ja"cent\, a. [L. adjacens, -centis, p. pr. of
   adjacere to lie near; ad + jac[=e]re to lie: cf. F.
   adjacent.]
   Lying near, close, or contiguous; neighboring; bordering on;
   as, a field adjacent to the highway. "The adjacent forest."
   --B. Jonson.
   [1913 Webster]

   Adjacent or contiguous angle. (Geom.) See Angle.
      [1913 Webster]

   Syn: Adjoining; contiguous; near.

   Usage: Adjacent, Adjoining, Contiguous. Things are
          adjacent when they lie close each other, not necessary
          in actual contact; as, adjacent fields, adjacent
          villages, etc.

                I find that all Europe with her adjacent isles
                is peopled with Christians.       --Howell.
          [1913 Webster] Things are adjoining when they meet at
          some line or point of junction; as, adjoining farms,
          an adjoining highway. What is spoken of as contiguous
          should touch with some extent of one side or the whole
          of it; as, a row of contiguous buildings; a wood
          contiguous to a plain.
          [1913 Webster]