soap plant

any of various plants some parts of which can be used as soap; esp., a tall W North American plant (Chlorogalum pomeridianum) of the lily family

See soap plant in American Heritage Dictionary 4

noun
  1. Any of several bulbous plants of the genus Chlorogalum of western North America, having small white or purple flowers. The edible bulbs of several species, especially C. pomeridianum, produce a soapy lather when crushed.
  2. Any of various plants having parts used as soap.
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