ˌcastor ˈoil BrE AmE noun [uncountable]
[ Date: 1700-1800 ; Origin: Probably from castor 'substance obtained from part of a beaver's body, used in medicines and perfumes' (16-19 centuries) , from castor 'beaver' (14-19 centuries) , from Latin , from Greek kastor ; because castor oil was once used instead of castor in medicines ]
a thick oil made from the seeds of a plant and used in the past as a medicine to make the ↑ bowel s empty