zy?go?gen?e?sis (?za? go??d??n ? s?s, ?z?g o?-) n. 1. the formation of a zygote. 2. reproduction by means of gametes. [1945?50] zy`go?ge?net?ic (-d???n?t ?k) adj. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.