The Collaborative International Dictionary of English v.0.48:

Plebeianism \Ple*be"ian*ism\, n. [Cf. F. pl['e]b['e]ianisme.]
   1. The quality or state of being plebeian.
      [1913 Webster]

   2. The conduct or manners of plebeians; vulgarity.
      [1913 Webster]