from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To focus one's aim; to zoom in and center on something.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- v. direct onto a point or target, especially by automatic navigational aids
- v. adjust (as by firing under test conditions) the zero of (a gun)
The phrase possibly comes from adjusting a sighting mechanism of a firearm to minimise the discrepancy between where the sight points and where a bullet lands on a target. (Wiktionary)