py·re·thrum (pī-rēthrəm, -rĕthrəm)
a. A Eurasian perennial plant (Tanacetum coccineum) in the composite family, cultivated for its colorful flower heads and formerly used as a source of an insecticide. Also called painted daisy.
b. A closely related perennial plant (Tanacetum cinerariifolium), commercially cultivated as the source of an insecticide.
2. An insecticide made from the dried flower heads of any of these plants.
[Latin, pellitory (Anacyclus pyrethrum), from Greek purethron, from pūr, fire (from its warming effect); see PYRETIC.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.