causticily

from The Collaborative International Dictionary of English v.0.48

Causticily \Caus*tic"i*ly\, n.
   1. The quality of being caustic; corrosiveness; as, the
      causticity of potash.
      [1913 Webster]

   2. Severity of language; sarcasm; as, the causticity of a
      reply or remark.
      [1913 Webster]