Definition of castor oil noun from the Oxford Advanced Learner's Dictionary


castor oil

BrE BrE//ˌkɑːstər ˈɔɪl//
; NAmE NAmE//ˌkæstər ˈɔɪl//
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a thick yellow oil obtained from a tropical plant and used in the past as a type of medicine, usually as a laxative Word Originmid 18th cent.: perhaps so named because it succeeded castor (an oily reddish brown substance) in medicinal use.
See the Oxford Advanced American Dictionary entry: castor oil