The adjustment of a gunsight for elevation and windage on a particular range under favorable light conditions WordNet 3.0 & Open English WordNet

In ranged weapons such as firearms and artillery pieces, sighting in or sight-in is a preparatory or corrective calibration of the sights with the goal that the projectile may be placed at a predictable impact position within the sight picture. Wikipedia

Adjusting firearms sights Wikipedia Disambiguation

action to place projectile at a predictable impact position Wikidata