In the book "Collectors Guide to Quilts" by Suzy McLennen Anderson, this is the definition she gives. "A quilt is defined as a bed covering, made of three layers of fabric (the top, the back, and the batting, or middle layer)."
Just thought I would throw this into the conversation. I consider a quilt anything a person (or doll, or animal) can cover with. There are a lot of 'quilted' items, but they are not all quilts, IMO. But there are no quilt police here so you can call quilted items whatever you want.