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1.                 From The Collaborative International Dictionary of English v.0.48:
                   
   
   
                   
                     
   Tetrazole \Tet*raz"ole\, n. [Tetrazo- + -ole.] (Org. Chem.)
      A crystalline acid substance, CH2N4, which may be regarded
      as pyrrol in which nitrogen atoms replace three CH groups;
      also, any of various derivatives of the same.
      [Webster 1913 Suppl.]