n (Celestial Objects) any of the planets Mercury, Venus, earth, and Mars, whose orbits lie inside the asteroid belt
in′ner plan′et
n. any of the four planets closest to the sun: Mercury, Venus, Earth, or Mars. [1950–55]
inner planet
inner planet
[¦in·ər ′plan·ət] (astronomy) Any of the four planets (Mercury, Venus, Earth, and Mars) in the solar system whose orbits are closest to the sun.ThesaurusSeeterrestrial planet