Definition of protoplanet
: a hypothetical whirling gaseous mass within a giant cloud of gas and dust that rotates around a sun and is believed to give rise to a planet
protoplanetaryplay \ˌprō-tō-ˈpla-nə-ˌter-ē\ adjective
First Known Use of protoplanet
Learn More about protoplanet
Britannica.com: Encyclopedia article about protoplanet
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