[pahy-ree-thrin, -reth-rin] 
| 1. | Also called pyrethrin I. a viscous, water-insoluble liquid, C2 1H2 8O3, extracted from pyrethrum flowers, used as an insecticide. |
| 2. | Also called pyrethrin II. a like compound, C2 2H2 8O5, obtained and used similarly. |
| py·re·thrin (pī-rē'thrĭn, -rěth'rĭn) n. Either of two viscous liquid esters, C21H28O3 or C22H28O5, that are extracted from pyrethrum flowers and used as insecticides. [pyrethr(um) + -in.] |
θrɪn