Definition of embryo sac
: the female gametophyte of a seed plant consisting of a thin-walled sac within the nucellus that contains the egg nucleus and other nuclei which give rise to endosperm on fertilization
First Known Use of embryo sac
Learn More about embryo sac
Britannica.com: Encyclopedia article about embryo sac
Seen and Heard
What made you want to look up embryo sac? Please tell us where you read or heard it (including the quote, if possible).