millstone
/ˈmɪlstəʊn/noun
1- each of two circular stones used for grinding corn磨石, 磨盘。
1.1
- figurative a heavy and inescapable responsibility〈喻〉重负, 重担：
she threatened to become a millstone round his neck.
她威胁要成为套在他脖子上的沉重负担。