Hmm, I think it is... at least by the pharmacology definition it is.. especially since it is used quite often medically, and a new Harvard study found that the THC in weed can help prevent cancer.
a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being.
a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being.