Noun

1. A black colloidal substance consisting wholly or principally of amorphous carbon and used to make pigments and ink
2. Destructive diseases of plants (especially cereal grasses) caused by fungi that produce black powdery masses of spores
3. Any fungus of the order ustilaginales
4. An offensive or indecent word or phrase
5. Creative activity (writing or pictures or films etc.) of no literary or artistic value other than to stimulate sexual desire

Verb

1. Make obscene
2. Stain with a dirty substance, such as soot
3. Become affected with smut
4. Affect with smut or mildew, as of a crop such as corn