thimbleweed

[thim-buh l-weed]
noun
  1. any of several plants having a thimble-shaped fruiting head, especially either of two white-flowered North American plants, Anemone riparia or A. virginiana.

Origin of thimbleweed

An Americanism dating back to 1825–35; thimble + weed1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for thimbleweed

thimbleweed

noun
  1. US any of various plants having a thimble-shaped fruit, esp an American anemone, Anemone virginiana, and a rudbeckia, Rudbeckia laciniata
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012