Redan
Redan (r?*d?n") , noun
[French, for Old French redent a double notching or jagging, as in the teeth of a saw, from Latin pref. re- re- + dens, dentis, a tooth. Compare Redented.]
1.
(Fortification) A work having two parapets whose faces unite so as to form a salient angle toward the enemy.
2.
A step or vertical offset in a wall on uneven ground, to keep the parts level.