Dictionary.net

• The reading of the leveling staff in its unchanged position when the leveling instrument has been taken to a new position; a sight directed backwards to a station previously occupied. Cf. Foresight, n., 3.

2010 - New Age Dictionary Database
By Oddity Software

• The reading of the leveling staff in its unchanged position when the leveling instrument has been taken to a new position; a sight directed backwards to a station previously occupied. Cf. Foresight, n., 3.

1913 - Webster's Revised Unabridged Dictionary
By Noah Webster.