The Collaborative International Dictionary of English v.0.48:

Purging \Pur"ging\, a.
   That purges; cleansing.
   [1913 Webster]

   Purging flax (Bot.), an annual European plant of the genus
      Linum (Linum catharticum); dwarf wild flax; -- so
      called from its use as a cathartic medicine.
      [1913 Webster]