I totally get you, I frequently see things in reverse like that. Often drives people around me nuts. (whereupon, they "join" me) :mrgreen:
I would think here on QB, it means glue that washes out.
Like, quilters who glue bindings, then sew them, then wash them. (which I intend to try) They want the glue to wash out.
You give washable markers to kids, which means non-permanant, and oopsies will wash out of the carpet, clothing, etc.