noun.
The cell formed by the union of two gametes, especially a fertilized ovum before cleavage.
noun.
The organism that develops from a zygote.
The Century Dictionary and Cyclopedia
noun.
Same as zygospore.
noun.
In biology, a fertilized ovum, or the equivalent, in plants and in unicellular organisms, of a fertilized egg; the product of the conjugation of gametes, or sexual cells.