ricinoleic acid \ric`in*o"le*ic ac"id\, n. (Chem.) An organic acid ({C18H34O3}) obtained from the castor-oil plant ({Ricinus communis}, or {Palma Christi}) and other species of the family {Euphorbiaceae}; chemicaly it is d-12-hydroxyoleic acid ({CH3(CH2)5.CH(OH).CH2.CH=CH.(CH2)7COOH}). Formerly called {palmic acid}. [1913 Webster +PJC]