mortar boardBrE /ˈmɔːtə bɔːd/ 🔊NAmE /ˈmɔːrtər bɔːrd/ 🔊 nouna black hat with a stiff square top, worn by some university teachers and students at special ceremonies 学位帽,方顶帽(大学师生在一些隆重场合戴的黑色帽) ➡ compare cap noun (3)