grindstone
noun /ˈɡraɪndstəʊn/
/ˈɡraɪndstəʊn/
Idioms - a round stone that is turned like a wheel and is used to make knives and other tools sharp
磨石；砂轮
Idioms
keep your nose to the grindstone
- (informal) to work hard for a long period of time without stopping
连续辛勤地工作