rə̇.ˈtrȯrˌsēn, -_sə̇n noun
( -s )
Etymology: New Latin retrorsus (specific epithet of Senecio retrorsus ) (from Latin, bent backwards) + English -ine
: a poisonous crystalline alkaloid C 18 H 25 NO 6 found in various plants of the genus Senecio (as S. retrorsus )