One of the terms label printers use that nobody else understands is ‘matrix’.  Matrix is the waste material pulled away from the label stock after labels are diecut on press:

Most all of our labels are diecut on press, right after the printing is done, so all production is done in one efficient operation.  The ‘matrix’ in this photo is being pulled up away from the labels and wound on a spool for disposal.  This is also known as the webbing, or the matrix waste.