line of sight

Also called line of sighting. an imaginary straight line running through the aligned sights of a firearm, surveying equipment, etc.

Astronomy. an imaginary line from an observer to a celestial body, coincident with the path traveled by light rays receivedfrom the body.

Radio. a straight line connecting two points sufficiently high and near one another so that the line is entirely above the surface of the earth.

Ophthalmology. line of vision.

sightline.

Origin of line of sight

First recorded in 1550–60

There were other instruments in other line-of-sight positions, very far away.

Operation Terror |William Fitzgerald Jenkins
I'm inclined like everybody else to consider perception on a line-of-sight basis instead of on a sort of all-around grasp.

Highways in Hiding |George Oliver Smith
He started the fuel pumps winding up, and swung the ship to point normal to the line-of-sight to the jammer.

Pushbutton War |Joseph P. Martino

line of sight

the straight line along which an observer looks or a beam of radiation travels

ophthalmol another term for line of vision