Glacis

[1] Glacises, also called taluses, were incorporated into medieval fortifications to strengthen the walls against undermining, to hamper escalades and so that missiles dropped from the battlements would ricochet off the glacis into attacking forces.

Glacis consisting of earthen slopes faced with stones were placed in front of the curtain walls and bastions (towers) to absorb the impact of cannon shots or to deflect them.

On natural, level ground, troops attacking any high work have a degree of shelter from its fire when close up to it; the glacis consists of a slope with a low grade inclined towards the top of the wall.

[4] The term glacis plate describes the sloped front-most section of the hull of a tank or other armored fighting vehicle,[6] often composed of upper and lower halves.

Sloped armour has two advantages: many projectiles will deflect rather than penetrate; those that attempt to will have to travel on a longer diagonal route through any given thickness of armor than if it were perpendicular to their trajectory.