What is Viable?

Legal Definition
Vitae habilis, capable of living. This is said of a child who is born alive in such an advanced state of formation as to be capable of living. Unless be is born viable he acquires no rights and cannot transmit them to his heirs, and is considered as if he bad never been born.

2. This term is used In the French law, Toull. Dr. Civ. Fr. tome 4, p. 101 it would be well to engraft it on our own Vide Traill. Med. Jur. 46, and Dead Born.
-- Bouviers Law Dictionary
Legal Definition
Capable of life. This term is applied to a newly-born ihfant, and especially to one prematurely born, which Is not only bom alive, but in such a state of organic development as to make possible the continuance of its Ilfe.
-- Black's Law Dictionary