Demi-bastion

Chambers's Encyclopaedia, Volume 3: Catarrh to Dion, p. 745

Demi-bastion, in Fortification, differs from a Bastion (q.v.) in having only one flank instead of two and no curtain.

A diagram of a demi-bastion, which is a triangular fortification structure with a single flank and no curtain.
Demi-bastion.
Source scan(s): p. 0756