Source : Webster's Revised Unabridged Dictionary (1913)

Saponaceous \Sap`o*na"ceous\, a. [L. sapo, -onis, soap, of
   Teutonic origin, and akin to E. soap. See {Soap}.]
   Resembling soap; having the qualities of soap; soapy.

   Note: Saponaceous bodies are compounds of an acid and a base,
         and are in reality a kind of salt.

Source : WordNet®

saponaceous
     adj : having the qualities of soap (and liable to slip away) [syn:
            {soapy}]