Source : Webster's Revised Unabridged Dictionary (1913)

Tracing \Tra"cing\, n.
   1. The act of one who traces; especially, the act of copying
      by marking on thin paper, or other transparent substance,
      the lines of a pattern placed beneath; also, the copy thus
      producted.

   2. A regular path or track; a course.

   {Tracing cloth}, {Tracing paper}, specially prepared
      transparent cloth or paper, which enables a drawing or
      print to be clearly seen through it, and so allows the use
      of a pen or pencil to produce a facsimile by following the
      lines of the original placed beneath.

Source : WordNet®

tracing paper
     n : a semitransparent paper that is used for tracing drawings