n 1  :  any of several chrysanthemums with finely divided often aromatic leaves including ornamentals as well as important sources of insecticides  2  :  an insecticide consisting of or derived from the dried heads of any of several Old World chrysanthemums (genus Chrysanthemum of the family Compositae) .
 
   
 
Similar sounding terms:  hy·per·ther·mia 
 
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