The word "blastulas" refers to the early stages of development of embryo in animals. These stages include the formation of a hollow sphere of cells that will eventually develop into different organs and tissues. There are several synonyms for the word "blastulas" including blastocyst, early embryonic stage, and pre-implantation stage. Other related terms include zygote, embryo, and fetus. Understanding the various stages of development in animals is important for both scientific research and medical applications. As such, there are many different terms that describe the complex processes involved in embryonic development and the transformation of cells into functional tissues and organs.