flatten vs graffiti

flatten

verb
  • To combine (separate layers) into a single image. 

  • To reduce (a data structure) to one that has fewer dimensions, e.g. a 2×2 array into a list of four elements. 

  • To press one's body tightly against a surface, such as a wall or floor, especially in order to avoid being seen or harmed. 

  • To knock down or lay low. 

  • To make something flat or flatter. 

  • To lower by a semitone. 

  • To be knocked down or laid low. 

  • To become flat or flatter; to plateau. 

  • To make vapid or insipid; to render stale. 

graffiti

verb
  • To mark a surface with such images. 

noun
  • Drawings or words drawn on a surface in a public place, usually made without authorization. 

  • Informal inscriptions, figure drawings, etc., as opposed to official inscriptions. 

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