Từ điển Hán Nôm

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