Breastwork is a built structure used as a support or as part of a defensive wall. “He caused a breastwork to be built” before seats set apart for high priests, so they could “rest their bodies and their arms upon” it while they spoke to his people (Mosiah 11:11).
A breastwork of timbers was built upon the inner bank of a ditch at the city of Bountiful. Workers cast dirt from the ditch “against the breastwork of timbers” and encircled the city with “a strong wall of timbers and earth” (Alma 53:4).