noun (n)

• a basis for comparison; a reference point against which other things can be evaluated(noun.communication)

  Synonym:
  criterion, measure, standard
  

  source: wordnet30
• Lydian stone; basanite; -- so called because used to test the purity of gold and silver by the streak which is left upon the stone when it is rubbed by the metal. See Basanite.(noun)

  source: webster1913