The Collaborative International Dictionary of English v.0.48:

Adjoin \Ad*join"\, v. t. [imp. & p. p. Adjoined; p. pr. & vb.
   n. Adjoining.] [OE. ajoinen, OF. ajoindre, F. adjoindre,
   fr. L. adjungere; ad + jungere to join. See Join, and cf.
   Adjunct.]
   To join or unite to; to lie contiguous to; to be in contact
   with; to attach; to append.
   [1913 Webster]

         Corrections . . . should be, as remarks, adjoined by
         way of note.                             --Watts.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Adjoin \Ad*join"\ ([a^]d*join"), v. i.
   1. To lie or be next, or in contact; to be contiguous; as,
      the houses adjoin.
      [1913 Webster]

            When one man's land adjoins to another's.
                                                  --Blackstone.
      [1913 Webster]

   Note: The construction with to, on, or with is obsolete or
         obsolescent.
         [1913 Webster]

   2. To join one's self. [Obs.]
      [1913 Webster]

            She lightly unto him adjoined side to side.
                                                  --Spenser.
      [1913 Webster]

WordNet (r) 3.0 (2006):

adjoin
    v 1: lie adjacent to another or share a boundary; "Canada
         adjoins the U.S."; "England marches with Scotland" [syn:
         border, adjoin, edge, abut, march, butt, butt
         against, butt on]
    2: be in direct physical contact with; make contact; "The two
       buildings touch"; "Their hands touched"; "The wire must not
       contact the metal cover"; "The surfaces contact at this
       point" [syn: touch, adjoin, meet, contact]
    3: attach or add; "I adjoin a copy of your my lawyer's letter"

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "adjoin":
   abut, abut on, add, affix, agglutinate, annex, append, appose,
   attach, be contiguous, be in contact, befringe, bind, border,
   border on, bound, bring near, burden, butt, communicate,
   complicate, conjoin, connect, decorate, edge, encumber, end,
   enframe, frame, fringe, glue on, hem, hitch on, infix, join,
   join with, juxtapose, juxtaposit, lap, lie by, line, list, march,
   marge, margin, marginate, meet, neighbor, ornament, paste on, plus,
   postfix, prefix, purfle, purl, put with, rim, run into,
   saddle with, set off, side, skirt, slap on, stand by, subjoin,
   suffix, superadd, superpose, tack on, tag, tag on, touch, trim,
   unite with, verge, verge upon