a tall plant, Ricinus communis, of the spurge family, cultivated for its ornamental foliage and having poisonous seeds that are the source of castor oil.
Main Entry: castor–oil plant Function: noun : a tropical Old World herb of the genus Ricinus (R. communis) widely grown as an ornamental or for itsoil-rich castor beans that are a source of castor oil
[kas-ter-oil, kah-ster-] 
tərˈɔɪl