A deflection point was a location from which a celestial object such as an asteroid was deflected away from another celestial body such as a planet.
In 2268 after the away team arrived on Amerind, Commander Spock noted that they would have to warp out of orbit within thirty minutes in order to divert an asteroid on a collision course with the planet. Every second delayed arriving at the deflection point would only compound the problem, perhaps past a solution. By stardate 4843.6, the USS Enterprise had been en route to the asteroid for several hours, and because of their delay on Amerind's surface, it was imperative to proceed at maximum warp speed for a period which exceeded the recommended safety margin in order to reach the deflection point in time. Upon reaching the deflection point, Spock ordered the activation of deflectors but the deflector beam was not powerful enough and only resulted in a degree of deflection by 0.0013 degrees. (TOS: "The Paradise Syndrome")