incurvation vs spiral

incurvation

noun
  • A curving inwards; the condition of being curved inwards. 

  • The act of acquiring or being given a curved form; an instance of curving or bending. 

  • The state of being curved or bent; any curved shape or formation; curvature; a curve; a bend. 

spiral

noun
  • A curve that is the locus of a point that rotates about a fixed point while continuously increasing its distance from that point. 

  • A helix. 

  • A section of track that forms a circle and crosses over itself, used for gaining height in mountainous territory. 

  • A self-sustaining process with a lot of momentum involved, so it is difficult to accelerate or stop it at once. 

verb
  • To increase continually. 

  • To cause something to spiral. 

  • To move along the path of a spiral or helix. 

adj
  • Helical, like a spiral. 

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