Boresight
Also: Bore Sighting
A rough first alignment of the sight or scope to the bore, done before live fire to get the first shots on paper.
Boresighting points the optic at the same place the barrel is already pointing, before you ever fire. On a bolt gun you can do it by eye: pull the bolt, rest the rifle steady, look through the bare bore at a distant mark, then adjust the scope to that same mark without moving the rifle. A laser or collimator does the same job mechanically.
Boresighting is not a zero, and it should not be mistaken for one. It only gets your first rounds onto the paper at 100 yards so you are not chasing misses off the target. You still have to fire and adjust to establish a true zero.