Definitions for backsight
The rear sight of a firearm.
A measurement or reading taken back towards a point of known elevation, used to calculate the height of the theodolite.
A measurement of a previously shot point, used to set the angle to zero when occupying a new position.
To shoot a backsight.
Origin: From the back + sight
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