1. A business venture which one spends vast amounts of money on, and recieves no returns from it.
2. An object or item which one spends a lot of money on, especially if the item or object does not serve its purpose correctly.
"I bought this 16 inch thermo-fan for my Datsun but it doesn't fit. I think it's a donkey."
"What did it cost you?"
"Not willing to tell."