I usually describe it as an unfinished project that you will very likely never go back to! Or at least, will only go back to kicking and screaming! I find that the reason for this is because that project became work instead of fun. This can happen for many reasons, you hit a real design problem, the colors aren't working right, your blocks are not coming together - it just isn't right. We usually quilt because we want to, when we have to work on something or force ourselves to work on it, it isn't worth it. So it goes on a shelf. There are so many projects we still really want to do and time is limited.