from Crazy Quilts by Penny McMorris:
Victorian quilt made of fancy dress fabrics and embellished with areas of decorative embroidery

from Webster's New World Dictionary:
quilt made of pieces of cloth of various colors and irregular shapes and sizes

from The Crazy Quilt Handbook by Judith Montano:
a method of haphazardly appliqueing bits and pieces of fabric to whole cloth, then covering each seam with decorative details and embroidery

My own definition:
a combination of embroidery stitches and embellishments sewn onto fabric, often scraps laid onto a ground, in a pleasing pattern of textures and colors