A slur is a smudged or elongated impression caused by slippage between the paper and the inked plate or blanket at the exact moment of ink transfer. It typically happens when cylinders are improperly packed, causing a mismatch in surface speeds, or when the paper shifts slightly in the grippers. The result is a directional blur that degrades halftone dots into ovals and makes fine text look muddy.
Heard on the job
Check your blanket packing, I'm seeing a bad slur on the trailing edge of the cyan sheet.
Insider tip
You can tell a slur from a double impression by looking at halftone dots under a loupe: a slur stretches the dot into a teardrop shape, while a double impression shows two distinct dots.