planetesimalPronunciation: /ˌplanɪˈtɛsɪm(ə)l/ AstronomyDefinition of planetesimal noun a minute planet; a body which could come together with many others under gravitation to form a planet. adjective denoting or relating to planetesimals: the planetesimal material orbiting the sunOrigin: early 20th century: from planet, on the pattern of infinitesimalplanetesimal in other Oxford dictionaries Definition of planetesimal in the US English dictionary
