The American Heritage® Dictionary of the English Language, 4th Edition
n. The product of conception at any point between fertilization and birth. It includes the embryo or the fetus as well as the extraembryonic membranes.
n. The fetus or embryo, including all the surrounding tissues protecting and nourishing it during pregnancy.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. an animal organism in the early stages of growth and differentiation that in higher forms merge into fetal stages but in lower forms terminate in commencement of larval life
Word Usage
"The conceptus from the very beginning is a human reality."