white elephant

Từ điển Oxford Advanced Learner 8th

ˌwhite ˈelephant [white elephant] BrE NAmE noun usually singular
a thing that is useless and no longer needed, although it may have cost a lot of money
•The new office block has become an expensive white elephant. From the story that in Siam (now Thailand) the king would give a white elephant as a present to somebody that he did not like. That person would have to spend all their money on looking after the rare animal.