any of a genus (Anagallis) of plants of the primrose family, esp. the (A. arvensis), with red, white, or blue, starlike flowers which close in bad weather
See pimpernel in American Heritage Dictionary 4
(pĭmˈpər-nĕlˌ, -nəl)
noun
Any of various plants of the genus Anagallis, especially the scarlet pimpernel (A. arvensis) having opposite, entire leaves and small red, purple, or white flowers.