pronucleus
noun
pro·nu·cle·us (ˌ)prō-ˈnü-klē-əs 
-ˈnyü-
: the haploid nucleus of a male or female gamete (such as an egg or sperm) up to the time of fusion with that of another gamete in fertilization
Example Sentences
Recent Examples on the Web Pronuclear transfer is the easier and cheaper method since the pronucleus is larger and easier to image and transfer than the spindle. 
Radhika Viswanathan, Vox, 24 July 2018
Radhika Viswanathan, Vox, 24 July 2018 Word History
Etymology
New Latin
First Known Use
1876, in the meaning defined above
Medical Definition
pronucleus
noun
pro·nu·cle·us (ˈ)prō-ˈn(y)ü-klē-əs
plural pronuclei -klē-ˌī also pronucleuses
also pronucleuses : the haploid nucleus of a male or female gamete (as an egg or sperm) up to the time of fusion with that of another gamete in fertilization see female pronucleus, male pronucleus