millstone

/M IH1 L S T OW0 N/
noun
  1. 1

    A large round stone used for grinding grain.

  2. 2

    A coarse-grained sandstone used for making such stones; millstone grit.

  3. 3

    Often in a millstone round one's neck (referring to Matthew 18:6 in the Bible): a heavy responsibility that is difficult to bear.

    โ€œPaying the mortgage every month is a millstone round their necks.โ€

Source: https://en.wiktionary.org/wiki/millstone