A poisonous glucoside found in many plants, as in the root of soapwort (
Saponaria), in the bark of soap bark (
Quillaia), etc. It is extracted as a white amorphous powder, which occasions a soapy lather in solution, and produces a local anæsthesia. Formerly called also
struthiin,
quillaiin,
senegin,
polygalic acid, etc. By extension, any one of a group of related bodies of which saponin proper is the type. [
1913 Webster]