smut

Short definition from Wiktionary

Noun

1. 1
   Soot.
2. 2
   A flake of ash or soot.
3. 3
   Sexually vulgar material; something that is sexual in a dirty way; pornographic material.
4. 4
   Obscene language; ribaldry; obscenity.
5. 5
   Any of a range of fungi, mostly Ustilaginomycetes, that cause plant disease in grasses, including cereal crops; the disease so caused.
6. 6
   Bad, soft coal containing earthy matter, found in the immediate locality of faults.
7. 7
   A copper boiler.

Verb

1. 1
   To stain (or be stained) with soot or other dirt.
2. 2
   To taint (grain, etc.) with the smut fungus.
3. 3
   To become tainted by the smut fungus.
4. 4
   To clear of the smut fungus.