/ Dictionary / Index C castor oil: Meaning and Definition of Find definitions for: cas'tor oil' Pronunciation: [key] a colorless to pale yellow, viscid liquid, usually obtained from the castor bean by a pressing process: used as a lubricant, in the manufacture of certain soaps and creams, and in medicine chiefly as a cathartic. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. castoreum castor-oil plant Related Content Daily Word Quiz: fresco Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language