(1):

(n.) 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.

(2):

(n.) The act or operation of making level.

(3):

(p. pr. & vb. n.) of Level