|Origin:||planete, from Late Latin planeta, from Greek planes 'wanderer'|
a very large round object in space that moves around the sun or another star: ! Do not say 'in a planet'. Say on a planet.
Mercury is the smallest of all the planets.
Is there life on other planets?
the future of Planet Earth
2, what planet is somebody on? spoken
used humorously to say that someone's ideas are not at all practical or sensible:
He thinks motherhood is glamorous - what planet is he on?
the world - used especially when talking about the environment:
a safer future for the planet
—planetary adjective [only before noun]WORD FOCUS: space
the planetary system
vehicles used in space: spaceship, spacecraft, rocket, (space) shuttle, probe, satellite, space station
someone who travels in space: astronaut, cosmonaut Russian
parts of a rocket's journey: countdown, launch, blast-off/take-off/lift-off, leaving the earth's atmosphere, going into orbit, re-entering the earth's atmosphere, splashdown/touchdown
places and things in space: planet, moon, star, sun, satellite, solar system, constellation, galaxy, universe, the cosmos, black hole, quasar, comet, meteor, asteroid
the study of space: astronomyspace
➔ See also space