What does "smut" mean?

Additional senses

1. 2.(Bot.) An affection of cereal grains producing a swelling which is at length resolved into a powdery sooty mass. It is caused by parasitic fungi of the genus Ustilago. Ustilago segetum, or U. Carbo, is the commonest kind; that of Indian corn is Ustilago maydis.
2. 3.Obscene language; ribaldry; obscenity. He does not stand upon decency . . . but will talk smut, though a priest and his mother be in the room. Addison. Smut mill, a machine for cleansing grain from smut.
3. 4.To stain or mark with smut; to blacken with coal, soot, or other dirty substance.
4. 5.To taint with mildew, as grain. Bacon.
5. 6.To blacken; to sully or taint; to tarnish.
6. 7.To clear of smut; as, to smut grain for the mill.
7. 8.To gather smut; to be converted into smut; to become smutted. Mortimer.
8. 9.To give off smut; to crock.