protoplanet

[proh-toh-plan-it]

Origin of protoplanet

First recorded in 1945–50; proto- + planet
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for protoplanet

protoplanet

noun
  1. a planet in its early stages of evolution by the process of accretion
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for protoplanet
n.

1949, from proto- + planet.

Online Etymology Dictionary, © 2010 Douglas Harper