mortarboard

UK: /ˈmɔːtəˌbɔːd/ US: /ˈmɔrtɚˌbɔrd/ ,(môr′tər bôrd′, -bōrd′)

WordReference Random House Learner's Dictionary of American English © 2025

mor•tar•board /ˈmɔrtɚˌbɔrd/   n. [countable]

1. a board, usually square, used by masons to hold mortar.
2. Education a close-fitting cap with a square, flat top and a tassel, worn at formal academic ceremonies by graduates or faculty.

WordReference Random House Unabridged Dictionary of American English © 2025

mor•tar•board  (môr′tər bôrd′, -bōrd′), n. 

1. a board, usually square, used by masons to hold mortar.
2. Education Also called cap. a cap with a close-fitting crown surmounted by a stiff, flat, square piece from which a tassel hangs, worn as part of academic costume.

• mortar² + board 1850–55

Collins Concise English Dictionary © HarperCollins Publishers::

mortarboard / ˈmɔːtəˌbɔːd/ noun

1. a black tasselled academic cap with a flat square top covered with cloth
2. Also called: hawk a small square board with a handle on the underside for carrying mortar