Definition of arris in English:

arris

Pronunciation /ˈerəs/ /ˈɛrəs/

noun

Architecture
  • A sharp edge formed by the meeting of two flat or curved surfaces.

    • ‘He noticed the two arris hip tiles that had fallen and saw that two adjacent tiles had become dislodged.’

Origin

Late 17th century alteration of early modern French areste ‘sharp ridge’, earlier form of arête.