Examples from the Web for mortarboard
Backstage earlier, McCaskill had given me tips on how to bobby pin the mortarboard cap to my head.
As for the mortarboard and gown, undergraduate opinion rather requires that they be left behind.An American at Oxford|John Corbin
Mr. Worthington pushed back his mortarboard and revealed the crimson chevron which it had bitten into his bald brow.
A right instinct sent him tiptoe over his lawn, another made him doff his mortarboard.
British Dictionary definitions for mortarboard
Word Origin and History for mortarboard
also mortar-board, "academic cap," 1854, probably from mortar (1) + board (n.1); so called because it resembles a mason's square board for carrying mortar. Earlier it was called a mortar cap (1680s) or simply morter (c.1600), from French mortier.