noun
a term referring to puzzle dust which is the particulate of paper fibre that is produced when puzzle pieces are being cut; pust is the detritus that collects and settles in the bag with the puzzle pieces during bagging and handling. Pust is commonly a source of annoyance for avid puzzlers, who typically sift pust from the puzzle pieces before starting any puzzle.
Pust flew everywhere when I opened the puzzle bag, and then settled on the bottom of the box.