Definitions

1. noun

An observation or measurement taken to check the accuracy of a preceding observation or measurement, especially in surveying or navigation.

“The astronomer took a backsight to verify the position of the star.”

2. noun

The rear or upper part of a ship or aircraft, especially the area above the stern or tail.

“The lookout stood at the backsight of the ship, scanning the horizon for any signs of danger.”

3. noun

A second observation taken after a first, to check the accuracy of the first observation.

“The surveyor took a second backsight to confirm the location of the boundary.”