I think the quilting organizations have more evolving and accurate definitions than general dictionaries. These are the people who know best what is going on in the quilt world today.
The American Quilter's Society (AQS) says:
the generally accepted definition of a quilt, i.e., a layer of batting between 2 layers of fabric, with some type of quilting or tying holding the layers together
The National Quilting Association (NQA) says:
Quilts must be made of fabric, have three layers, and contain quilting.
Quilts created as art quilts, reflecting innovative construction and design techniques, theme or subject matter and/or materials.
The Quilters' Guild of the British Isles says:
Definition of a quilt: The structure of a quilt is traditionally three complete layers but a minimum of two complete layers may be appropriate. Stitch or other elements must pierce these layers.
Studio Art Quilt Associates (SAQA) says:
a contemporary artwork exploring and expressing aesthetic concerns common to the whole range of visual arts: painting, printmaking, photography, graphic design, assemblage and sculpture, which retains, through materials or technique, a clear relationship to the folk art quilt from which it descends
A very wide range of ideas, don't you think? I say, if you call your work a quilt, then that's jolly well what it is! :D