from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A topical insecticide, C21H20CL2O3, used to treat head lice and nits, scabies, and various species of ticks.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A synthetic insecticide, C21H20Cl2O3, used to treat head lice, nits, scabies, and in flea collars.
per- + (res)methrin, a pyrethroid (resm-, of unknown origin + (pyr)ethrin).(American Heritage® Dictionary of the English Language, Fourth Edition)