A stain or smear left by something being smudged.(noun)
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Use "smudging" in a sentence
"This is called smudging in Native American traditions."
"I also use a ritual called smudging, which involves burning sage and cupping the smoke in my hands to waft it across the space as a way to cleanse it."
"The smudging is a problem if you don't allow the ink to dry, and using highlighters will wet the ink again causing smudges; so if you highlight your notes, use the highlighter before you write with these pens, and left handed writers may have problems with them."