lit. to penetrate into a bull's horn (idiom); fig. to waste time on an insoluble or insignificant problem / to bash one's head against a brick wall / a wild goose chase / a blind alley / to split hairs
lit. honing a bull's horn; fig. to waste time on an insoluble or insignificant problem / to bash one's head against a brick wall / a wild goose chase / a blind alley / to split hairs / same as idiom 鑽牛角尖|钻牛角尖