Boresight
From Biocrawler, the free encyclopedia.
Imagine you are standing upright on the ground. If you look straight ahead you are looking "along boresight". The boresight direction of an antenna is usually taken to be the direction along which the radiation is most highly concentrated. There can be, therefore, more than one boresight direction (eg, a vertically orientated half-wave dipole has uniform radiation in the azimuth plane, and any direction in this azimuth plane may be defined as boresight.)
Source: http://www.ee.surrey.ac.uk/Personal/D.Jefferies/antennas.html
Another analogy is to think of it as like firing a gun. When you sight up a gun, you line up the bore or barrel in the direction you want the bullet to go; hence, 'boresight'. The antenna engineers have borrowed the term: it's the direction of maximum radiation.
