The number of degrees an aspect can be off and still be active. Orbs vary from one aspect to another, from 9 degrees for strong aspects like a conjunction to just a few degrees for weaker aspects.
Outer Planets :
The planets farthest out in the solar system. These move the slowest around the zodiac and have the deepest effects on our lives, mostly at an unconscious level. Includes Uranus, Neptune, and Pluto; Saturn and Chiron are often added to the list.