will-o'-the-wisp

剑桥词典

something that is impossible to get or achieve
虛幻的目標；實現不了的事
Full employment is the will-o'-the-wisp that politicians have been chasing for decades . 全民就業是政治家們幾十年來一直在追求的一個幻想。 返回 will-o'-the-wisp