leveling, n. [Written also levelling.].
The act or operation of making level. [1913 Webster]
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]
. 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.