A friend of mine posted this on a website. I think it defines what a rainbow baby is clearly.
Ã¢â‚¬Å“A Rainbow Baby is the understanding that the beauty of a rainbow does not negate the ravages of the storm. When a rainbow appears, it doesn't mean the storm never happened or that the family is not still dealing with its aftermath. What it means is that something beautiful and full of light has appeared in the midst of the darkness and clouds. Storm clouds may still hover but the rainbow provides a counterbalance of color, energy and hopeÃ¢â‚¬Â ~unknown~