a work consisting of half a bastion, and hence having one face and one flank.
Origin of demibastion
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
fortifications half a bastion, having only one flank, at right angles to the wall
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012