arris vs cusp

arris

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

  • A ridge formed on the surface of flaked stone, such as a arrowhead or hand axe, as the result of the intersection of two or more flake removals. 

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

  • Buttocks, arse. 

cusp

noun
  • A point made by the intersection of two curved lines or curved structures, a common motif in Gothic architecture. 

  • Any of the pointed parts of a canine tooth or molar. 

  • A point of transition. 

  • A flap of a valve of a heart or blood vessel. 

  • A boundary between zodiacal signs and houses. 

  • A point of a curve where the curve is continuous but has no derivative, but such that it has a derivative at every nearby point. 

  • A sharp point or pointed end. 

  • An important moment when a decision is made that will determine future events. 

verb
  • To behave in a reckless or dangerous manner. 

How often have the words arris and cusp occurred in a corpus of books? (source: Google Ngram Viewer )