The Collaborative International Dictionary of English v.0.48:

Adjunction \Ad*junc"tion\, n. [L. adjunctio, fr. adjungere: cf.
   F. adjonction, and see Adjunct.]
   The act of joining; the thing joined or added.
   [1913 Webster]

WordNet (r) 3.0 (2006):

adjunction
    n 1: an act of joining or adjoining things [syn: junction,
         adjunction]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

ADJUNCTION. in civil law. Takes place when the thing belonging to one person
is attached or united to that which belongs to another, whether this union is

caused by inclusion, as if one man's diamond be encased in another's ring;
by soldering, as if one's guard be soldered on another's sword; by sewing,
as by employing the silk of one to make the coat of another; by
construction; as by building on another's land; by writing, as when one
writes on another's parchment; or by painting, when one paints a picture on
another's canvas.
     2. In these cases, as a general rule, the accessory follows the
principal; hence these things which are attached to the things of another
become the property of the latter.  The only exception which the civilians
made was in the case of a picture, which although an accession, drew to
itself the canvas, on account of the importance which was attached to it.
Inst. lib. 2, t. 1, Sec. 34; Dig. lib. 41, t. 1, 1. 9, Sec.  2. See
Accession, and 2 Bl. Comm. 404; Bro. Ab. Propertie; Com. Dig. Pleader, M.
28; Bac. Abr. Trespass, E 2. 1 Bouv. Inst. n. 499.