Planet X
/ˌplanɪt ˈɛks/Astronomy
noun
A hypothetical undiscovered planet in the solar system, whose supposed orbit lies beyond that of the outermost planet known; (originally) that identified as the ninth planet and named Pluto; (later) a hypothetical planet or planets beyond Pluto. Also (especially Science Fiction ): (an arbitrary designation for) an unknown or hypothetical alien planet.
Origin
Late 19th century. From planet + X.
- take a hammering
- take a hand
- take a hike
- take aim
- take a jerry to
- take a leaf out of someone's book
- take-all
- take a load off someone's mind
- take a lot of (or some) ——
- take a (or the) hint
- take a (or the) load off one's feet
- take-apart
- take a poke at someone
- take a poor view of
- take a powder
- take a rain check
- take a running jump
- take a shine to
- take a toss
- take a trip (or walk) down memory lane
- takeaway
- take away from
- take a wicket
- take a woman to wife
- take-back