slippery vs vitreous

slippery

adj
  • Of a surface, having low friction, often due to being covered in a non-viscous liquid, and therefore hard to grip, hard to stand on without falling, etc. 

  • Unstable; changeable; inconstant. 

  • Evasive; difficult to pin down. 

vitreous

adj
  • Having a shiny nonporous surface. 

  • Of or resembling glass; glassy. 

  • Of a semi-crystalline substance where the atoms exhibit short-range order, but without the long-range order of a crystal. 

  • Of or relating to the vitreous humor of the eye. 

noun
  • The vitreous humor. 

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