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 ]