white elephant

noun

1. a possession unwanted by the owner but difficult to dispose of: Our Victorian bric-a-brac and furniture were white elephants.
2. a possession entailing great expense out of proportion to its usefulness or value to the owner: When he bought the mansion he didn’t know it was going to be such a white elephant.
3. an abnormally whitish or pale elephant, usually found in Thailand; an albino elephant.