fetus(n = noun.animal)foetus - an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal;
The young or embryo of a vertebrate animal in the womb, or in the egg; often restricted to the later stages in the development of viviparous and oviparous animals. showing the main recognizable features of the mature animal, embryo being applied to the earlier stages. [1913 Webster]