the bitter aromatic bark of either of two South American trees (Galipea officinalis or Cusparia trifoliata) of the rue family, used as a medicinal tonic and as a flavoring in bitters
See angostura (bark) in American Heritage Dictionary 4
(ăngˌgə-sto͝orˈə, -styo͝orˈə)
noun
The bitter aromatic bark of either of two South American trees (Galipea officinalis or Cusparia trifoliata), used as a flavoring in bitters and as a tonic.