Rhamnus
noun
Rham·nus
| \ ˈram-nəs
\
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Medical Definition of Rhamnus
: a genus (family Rhamnaceae) of trees and shrubs that have small flowers and a fruit which is a drupe and that comprise the buckthorns (as cascara buckthorn, R. purshiana) of which some yield pigments or purgatives (as cascara sagrada)