Formally it is of French origin, and its meaning is "Jehovah is God".
A more up-to-date definition would be that of a kind-hearted and good friend. Her heart is bigger than most. She loves life and is a devoted companion and friend. There is nothing she wouldn't do for those she loves. She has a great sense of humor and her eyes sparkle when she laughs. To have a Joelle in your life is to be blessed!
I wish everyone was like Joelle.