From the A.Word.A.Day mailing list:
  1. A possession unwanted by the owner but difficult to dispose of.
  2. A possession entailing great expense out of proportion to its usefulness or value to the owner.
  3. An abnormally whitish or pale elephant, usually found in Thailand; an albino elephant.
{From the perhaps apocryphal tale that the King of Siam would award a disagreeable courtier with a white elephant, the upkeep of which would ruin the courtier.}

"Now an orchestra opening a new hall has reason to pray, solemnly and at length, that it will not be saddled with a white elephant with mediocre acoustics." Allan Kozinn, "A Venerable Concert Hall That's the Belle of the Ball," The New York Times, Sep 30, 2000.