What is the distance, reckoned toward the west, between the two meridians passing through the extremities of a course, or portion of a ship's path; the departure of a course which lies to the west of north called?

westing — The distance, reckoned toward the west, between the two meridians passing through the extremities of a course, or portion of a ship's path; the departure of a course which lies to the west of north. (Webster's 1913.)

Sources