noun
noun: smut; plural noun: smuts

    1.
    a small flake of soot or other dirt or a mark left by one.
    "all those black smuts from the engine"
    2.
    a fungal disease of cereals in which parts of the ear change to black powder.
    "a few bad crop years with smut and drought and frost"
    3.
    obscene or lascivious talk, writing, or pictures.
    "porn, in his view, is far from being harmless smut"