noun plan·e·tes·i·mal \ˌpla-nə-ˈte-sə-məl, -zə-məl\

Definition of planetesimal

  1. :  any of numerous small celestial bodies that may have existed at an early stage of the development of the solar system

Origin and Etymology of planetesimal

planet + -esimal (as in infinitesimal)

First Known Use: 1903

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