glacis

Etymology

Borrowed from French glacis (“slippery surface”), from Old French glacier (“to glide; to slide, slip”) + French -is (suffix forming nouns). Glacier is derived from Vulgar Latin *glaciare (“to slide, slip”), from Latin glaciāre, the present active infinitive of glaciō (“to freeze”), from Latin glaciēs (“ice”) (probably from Proto-Indo-European *gel- (“to be cold; to freeze”)) + -ō (suffix forming regular first-conjugation verbs). cognates * Medieval Latin glatia (“incline in front of a fortification”)

noun

1. A gentle incline.
   1. (geomorphology) A gentle sloping landform created by the deposition or erosion of material.
   2. (military)
      1. (architecture, also figurative) A gentle incline in front of a fortification which protects it from cannon fire and exposes attackers to more effective return fire from defenders.
      2. 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).
   3. (post) A device for sorting mail which slides parcels across a sloped surface.