Definition of "pyrethrum" [pyrethrum]

• Any of several Old World plants of the genus Chrysanthemum, such as C. coccineum, cultivated for their showy flower heads. (noun)
• An insecticide made from the dried flower heads of Chrysanthemum cinerariifolium or C. coccineum. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "This unique form of incense makes use of a natural plant compound called pyrethrum which is derived from Old World plants of the genus"
• "This unique form of incense makes use of a natural plant compound called pyrethrum which is derived from Old World plants of the genus Chrysanthemum."
• "Plant-derived and metallic insecticides such as pyrethrum, lead arsenate and copper sulfate had been tried but did not work well."