ARRIS

Etymology 1

Noun

arris (plural arrises)

A sharp edge or ridge formed by the intersection of two surfaces

(architecture) A sharp edge or ridge formed by the intersection of two curved surfaces

(archaeology) A ridge formed on the surface of flaked stone that results from the intersection of two or more flake removals. The arris marks the location of flake scars on the dorsal surface of chipped stone.

Etymology 2

Rhyming slang via Aristotle = bottle, then bottle and glass, then arse.

Noun

arris (plural arrises)

(Cockney rhyming slang) Buttocks, arse.

Source: Wiktionary

Ar"ris, n. Etym: [OF. areste, F. arête, fr. L. arista the top or beard of an ear of grain, the bone of a fish.] (Arch.)

Definition: The sharp edge or salient angle formed by two surfaces meeting each other, whether plane or curved; -- applied particularly to the edges in moldings, and to the raised edges which separate the flutings in a Doric column. P. Cyc. Arris fillet, a triangular piece of wood used to raise the slates of a roof against a chimney or wall, to throw off the rain. Gwilt.

– Arris gutter, a gutter of a V form fixed to the eaves of a building. Gwilt.

Source: Webster’s Unabridged Dictionary 1913 Edition