white elephant ˌwhite ˈelephant noun [countable]
something that is completely useless, even though it cost a lot of money:
• The hotel is unfinished and structurally unsound - a white elephant of epic proportions.
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white elephant UK US noun [C]
► something that costs a lot of money but has no useful purpose: »
The stadium is likely to become a white elephant after the championships are over.
Financial and business terms. 2012.