This is a made-up word being used by cloning researchers who want to distance their work from the abortion debates. The Kennedy-Feinstein bill implicitly endorsed this view by contending an embryo isn't worth protecting until it is implanted in a woman's womb. These are embryonic cells that have the potential to become anything-sort of like freshmen with undeclared majors. A totipotent cell could become a brain cell, or a bone cell, or a nose cell. They're the real attraction for researchers right now.
Scientists use transgenic sheep, for example, to produce medically useful proteins.