a tropical plant (Ricinus communis) of the spurge family, with seeds (castor beans) from which castor oil is extracted
See castor-oil plant in American Heritage Dictionary 4
(kăsˈtər-oilˈ)
noun
A poisonous, ornamental, tropical African herb or tree (Ricinus communis) having palmately lobed leaves and unisexual flowers and yielding a seed oil of commercial and medicinal value.