outer planet

noun Astronomy.

1. any of the four planets with orbits outside the orbit of Mars, namely, the planets Jupiter, Saturn, Uranus, and Neptune.

noun

1. any of the planets Jupiter, Saturn, Uranus, Neptune, and (formerly) Pluto, whose orbit lies outside the asteroid belt

1. Any of the four planets Jupiter, Saturn, Uranus, and Neptune, whose orbits lie outside that of Mars. The outer planets are large gas giants. Compare inner planet. See also superior planet.