A technical dictionary of printmaking, André Béguin.

• Slurring occurs when a freshly printed sheet of paper is put above another one. Slurring is particularly frequent when printed sheets are piled up, when the ink is not siccative enough, or if one does not slip sheet.
  Sometimes slurring can come about through excessive pressure or rubbing when the proofs are already dry (too tall a pile etc.)
• The result of movement during impression between type and paper producing a blurred impression.
  f maculer; frisotage; papillotage; regiflage (en impression en taille douce, ce mot se dit pour papillotage) d schmieren; abschmieren; schmitzen; Schmitz n vegen; smeren; smetten.