Top, Help, Feedback, Customize Type in a word below to find its rhymes, synonyms, definitions, and more: Word:  Find rhymes Find synonyms Find antonyms Find definition Appears in definition of Find related words Find similar sounding words Find homophones Check spelling of word Match consonants only Match these letters Search in Shakespeare Search for quotations Organize results by: Syllables Letters     Include phrases: Yes No Rhymes   Synonyms   [Definitions]   Homophones   Similar sound   Same consonants   Related Definitions of yolk sac: noun:   membranous structure enclosing the yolk of eggs in birds reptiles marsupials and some fishes; circulates nutrients to the developing embryo noun:   membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional Search for yolk sac at other dictionaries: OneLook, Answers.com, Merriam-Webster Search for yolk sac:    [Definition]   Quotes   Encyclopedia   Copyright © 2010 Datamuse