buchuPronunciation: /ˈbʌkuː/Definition of buchu noun a heather-like South African shrub which is cultivated for its essential oil and as an ornamental. Genus Agathosma (or Barosma) and Diosma, family Rutaceae [mass noun] a diuretic drug made from the powdered leaves of the buchu. Origin: mid 18th century: from Khoikhoi