The Collaborative International Dictionary of English v.0.48:

Junction \Junc"tion\, n. [L. junctio, fr. jungere, junctum, to
   join: cf. F. jonction. See Join.]
   [1913 Webster]
   1. The act of joining, or the state of being joined; union;
      combination; coalition; as, the junction of two armies or
      detachments; the junction of paths.
      [1913 Webster]

   2. The place or point of union, meeting, or junction;
      specifically, the place where two or more lines of railway
      meet or cross.
      [1913 Webster]

   Junction plate (Boilers), a covering or break-join plate
      riveted to and uniting the edges of sheets which make a
      butt joint.

   Junction rails (Railroads), the switch, or movable, rails,
      connecting one line of track with another.
      [1913 Webster]

WordNet (r) 3.0 (2006):

junction
    n 1: the place where two or more things come together
    2: the state of being joined together [syn: junction,
       conjunction, conjugation, colligation]
    3: the shape or manner in which things come together and a
       connection is made [syn: articulation, join, joint,
       juncture, junction]
    4: something that joins or connects [syn: junction,
       conjunction]
    5: an act of joining or adjoining things [syn: junction,
       adjunction]