white elephant
US /waɪt ˈɛl.ə.fənt/
UK /waɪt ˈɛl.ə.fənt/
1.
a possession that is useless or troublesome, especially one that is expensive to maintain or difficult to dispose of
:
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The old factory became a white elephant for the city, costing millions in upkeep.
•
Buying that huge mansion turned out to be a real white elephant.