v.1. To aim or focus something, such as a weapon or telescope, toward a specific target or location: The enemy spotted the approaching aircraft and zeroed in their missiles. Zero the telescopes in on the watchtower.
2. To identify with increasing accuracy a property of something, especially its location: We are finally zeroing in on the location of the smuggling ring.
3. To adjust the aim or sight of a weapon by repeated firings: The soldiers fired a few rounds in order to zero in their rifles. I zeroed the gun in at 100 yards.
4. zero in on To direct one's gaze or attention to something: The children zeroed in on the display of toys in the store window.