demigorge

from The Century Dictionary.

• noun In fort, that part of the polygon which remains after the flank is raised, and goes from the curtain to the angle of the polygon. It is half of the vacant space of or entrance into a bastion.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Fort.) Half the gorge, or entrance into a bastion, taken from the angle of the flank to the center of the bastion.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun military Half the gorge, or entrance into a bastion, taken from the angle of the flank to the centre of the bastion.