What does adjoin mean?
The definition of adjoin
Ad*join”, v. t.
[imp. & p. p. Adjoined; p. pr. & vb. n. Adjoining.]
Etym: [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. Corrections . . . should be, as remarks, adjoined by way of note. Watts.

Ad*join”, v. i.
1 To lie or be next, or in contact; to be contiguous; as, the houses adjoin. When one man’s land adjoins to another’s. Blackstone.

Note: The construction with to, on, or with is obsolete or obsolescent.

2 To join one’s self. [Obs.] She lightly unto him adjoined side to side. Spenser.