Definition of "pimpernel"

pimpernel

/ˈpɪmpənɛl/

noun
plural pimpernels
1. (now rare) A plant of the genus Pimpinella, especially burnet saxifrage (Pimpinella saxifraga).
2. Any of various plants of the genus Anagallis, having small red, white or purple flowers, especially the scarlet pimpernel (Anagallis arvensis).
  Quotations
  Common Pimpernel has diverse weak square stalks lying on the ground, beset all along with two small and almost round leaves at every joint [...].
  1653, Nicholas Culpeper, The English Physician Enlarged, Folio Society, published 2007, page 221
  Pimpernel (poor man's weather glass) was also a protection, but as the gatherer collected the herbs, he must chant a certain incantation and continue to do so twice a day for 15 days[.]
  1940, Rosetta E. Clarkson, Green Enchantments: The Magic Spell of Gardens, The Macmillan Company, page 272
3. Sanguisorba spp.
  1. Great burnet (Sanguisorba officinalis)
  2. Salad burnet (Sanguisorba minor).
4. (Canada, US) A yellow pimpernel (Taenidia integerrima)
5. (figurative) Someone resembling the fictional Scarlet Pimpernel; a gallant dashing resourceful man given to remarkable feats of bravery and derring-do in liberating victims of tyranny and injustice.