The Collaborative International Dictionary of English v.0.48:

Basil \Bas"il\, n. [F. basilic, fr. L. basilicus royal, Gr.
   basiliko`s fr. basiley`s king.] (Bot.)
   The name given to several aromatic herbs of the Mint family,
   but chiefly to the common or sweet basil (Ocymum
   basilicum), and the bush basil, or lesser basil (Ocymum
   minimum), the leaves of which are used in cookery. The name
   is also given to several kinds of mountain mint
   (Pycnanthemum).
   [1913 Webster]

   Basil thyme, a name given to the fragrant herbs Calamintha
      Acinos and Calamintha Nepeta.

   Wild basil, a plant (Calamintha clinopodium) of the Mint
      family.
      [1913 Webster]