If something is inviable, it can't survive or function as it should. An inviable animal, plant, or cell will not live long enough to mature or reproduce, and an inviable business will soon fail because it can't pay its bills.
Inviable is the opposite of viable, which may be a more familiar word. Many things can be inviable. An inviable seed will not grow if it is planted, and a bird's egg that is inviable will not hatch. Things that people create or plan can also be inviable. A school's sports program will be inviable if nobody wants to participate, or if there's no money for equipment, or if it's impossible for teams to practice because of scheduling conflicts.