glacis in Russian

A gentle incline.

(architectural element, also, figuratively) A gentle incline in front of a fortification which protects it from cannon fire and exposes attackers to more effective return fire from defenders.

In full glacis plate: the angled armour plate on the front of a tank which protects it from projectiles; also (often, nautical) , such a plate protecting an opening (for example, on a ship).