1. planetesimal

noun. one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system.


  • celestial body

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Example sentences of the word planetesimal

1. Noun, singular or mass
Some of these scientists began referring to Pluto as a planetesimal.

2. Adjective
One theory of how the moon was formed is that a planetesimal about the size of Mars hit the Earth and spun off a chunk of material that later became the moon.