Noun

1. Dough.
2. A stiff flour pudding, often with dried fruit, boiled in a cloth bag, or steamed
   • 1901, Henry Lawson, short story The Ghosts of Many Christmases, published in Children of the Bush http://www.gutenberg.org/etext/7065:

     The storekeeper had sent them an unbroken case of canned plum pudding, and probably by this time he was wondering what had become of that blanky case of duff.

Noun

1. Decaying vegetable matter on the forest floor.
2. Coal dust.
3. The bits left in the bottom of the bag after the booty has been consumed, like crumbs.
4. Something spurious or fake; a counterfeit, a worthless thing.
5. an 1800s baseball term meaning an error

Adjective

1. Worthless; not working properly, defective.

   Why do I always get a shopping trolley with duff wheels?

Verb

1. To disguise something to make it look new.
2. To alter the branding of stolen cattle; to steal cattle.
3. To beat (up).

   I heard Nick got duffed up behind the shopping centre at the weekend.

4. To hit the ground behind the ball.