n 1 a  cap  :  a small genus of perennial herbs (family Ranunculaceae) having two or three ternately divided serrate leaves and white flowers in long rodlike racemes - see BLACK COHOSH   b  :  a plant of the genus Cimicifuga  2  :  the dried rhizome and roots of black cohosh (Cimicifuga racemosa) that were formerly used as a sedative and alterative in the treatment of rheumatism and chorea - called also black cohosh root  .
 
 
 
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