Definition of duff:
"1901: 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. &mdash"
"why do I always get a shopping trolley with duff wheels?"
(abbrev) :
(insult) Dumb/Designated Ugly Fat Friend, an attractive woman's less attractive friend; (science fiction fandom) Down Under Fan Fund, a fan fund to bring Australasian members of
fandom to North America and vice versa, in alternating years