vitamin K

noun

Etymology: Named similarly to the other vitamins, that are named after their order of discovery. This one was assigned its "K" from Danish koagulation by the Danish researcher Henrik Dam. The sense that is a slang alias for ketamine is because of the initial letter of that drug's name, as also with the slang sense of Special K.

1. Any of several related fat-soluble vitamins, found in leafy green vegetables, essential for blood clotting.
2. The drug ketamine.