noun

• (uncountable) Soot.
• (countable) A flake of ash or soot.
  "She reached it soon after half-past two. She found its gloomy nineteenth-century façade, black with the smuts of ninety years, a little daunting, and mounted its broad steps in some trepidation. But she rang the bell hard and knocked firmly."
• (uncountable) Sexually vulgar material; something that is sexual in a dirty way; pornographic material.
  "It is no use to say, well, your anthrostate requires smut to be shielded, but your neighbor’s antrhostate^([sic]) says he can show anything anywhere. The neighbor’s behavior affects you, so you have to have the same rules."
• (uncountable) Obscene language; ribaldry; obscenity.
  "He does not stand upon decency […] but will talk smut, though a priest and his mother be in the room."

verb

• (ambitransitive) To stain (or be stained) with soot or other dirt.
  "it bears a very good Crop , and seldom smuts"
• (transitive) To taint (grain, etc.) with the smut fungus.
  "Mildew also falls upon Corn, and smuts it"
• (intransitive) To become tainted by the smut fungus.
  "It smutted to a far greater degree than the year before, say three fourths, or more. I obtained but little more than the seed sown, and that was handsome wheat. This failure I imputed to the same supposed cause which operated the last year."
• (transitive) To clear of the smut fungus.
  "to smut grain for the mill"