oo-(word root) eggExamples of words with the root oo-: oocyteAbused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embreeoo-pref. Egg; ovum: oogenesis.[Greek ?io-, from ?ion, egg; see awi- in Indo-European roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.oo- or oö-combining formegg or ovum: oosperm. [from Greek ?ion egg1]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014oo- a combining form meaning ?egg?: oogamete. [