A lot of people have asked me this question. The funny thing is that most people -- even non-quilters -- actually already know what they are, but they know them by a different name. Perhaps you've heard about left over quilt blocks? Or UFO's -- unfinished quilt objects?
I define Orphan Quilt Blocks as simply "quilt blocks that are not already in a finished quilt." This is a pretty broad definition which would include left over blocks, blocks in a quilt top never finished, single loose blocks, unfinished blocks, etc. Additionally, Orphan Quilt Blocks can be antique, vintage, contemporary or anything in-between.
For examples of Orphan Blocks, please check out my book, Orphan Block Quilts.