Millstone definition of millstone by The Free Dictionary
mill·stone (mĭl′stōn′) n. 1. One of a pair of cylindrical stones used in a mill for grinding grain. 2. a. A source of worry or distress: a responsibility that became a millstone. b. An obstacle to success. See Synonyms at burden. millstone (ˈmɪlˌstəʊn) n 1. (Tools) one of a pair of heavy flat discshaped stones that are rotated one against ...