A boomerang is a curved piece of wood which comes back to you if you throw it in the correct way. Boomerangs were first used by the people who were living in Australia when Europeans arrived there.
VERB
（計劃）起反作用，使自食其果
If a plan boomerangs, its result is not the one that was intended and is harmful to the person who made the plan.
例句
The trick boomeranged, though...然而這個花招竟害了自己。He risks defeat in the referendum which he called, but which threatens to boomerang against him.他冒著失敗的危險進行他所謂的“公投”，但這恐怕會反過來對他不利。