Source : Webster's Revised Unabridged Dictionary (1913)

Contact \Con"tact\, n. [L. contactus, fr. contingere, -tactum,
   to touch on all sides. See {Contingent}.]
   1. A close union or junction of bodies; a touching or
      meeting.

   2. (Geom.) The property of two curves, or surfaces, which
      meet, and at the point of meeting have a common direction.

   3. (Mining) The plane between two adjacent bodies of
      dissimilar rock. --Raymond.

   {Contact level}, a delicate level so pivoted as to tilt when
      two parts of a measuring apparatus come into contact with
      each other; -- used in precise determinations of lengths
      and in the accurate graduation of instruments.