The American Heritage® Dictionary of the English Language, 4th Edition
n. The innermost of the three primary germ layers of an animal embryo, developing into the gastrointestinal tract, the lungs, and associated structures. Also called hypoblast.
n. One of the three tissue layers in the embryo of a metazoan animal. Through development, it will produce the digestive system of the adult.
the GNU version of the Collaborative International Dictionary of English
n. The inner layer of the skin or integument of an animal.
n. The innermost layer of the blastoderm and the structures derived from it; the hypoblast; the entoblast. See Illust. of ectoderm.
The Century Dictionary and Cyclopedia
n. In zoology, the completed inner layer of cells in all metazoan animals, formed by the cells of the hypoblast or endoblast, and representing, under whatever modification, the lining of the enteron: opposed to ectoderm.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the inner germ layer that develops into the lining of the digestive and respiratory systems
Word Usage
"The endoderm is the innermost layer that lines the digestive tract."