The Collaborative International Dictionary of English v.0.48:

Leveling \Lev"el*ing\, n. [Written also levelling.]
   1. The act or operation of making level.
      [1913 Webster]

   2. (Surveying) The art or operation of using a leveling
      instrument for finding a horizontal line, for ascertaining
      the differences of level between different points of the
      earth's surface included in a survey, for establishing
      grades, etc., as in finding the descent of a river, or
      locating a line of railroad.
      [1913 Webster]

   Leveling instrument. See Surveyor's level, under Level,
      n.

   Leveling staff, a graduated rod or staff used in connection
      with a leveling instrument for measuring differences of
      level between points.
      [1913 Webster]