- any of a large class of organic, nitrogen-containing ring compounds of vegetable origin and sometimes synthesized, some of which are liquid but most of which are solid, that have a bitter taste, that are usually water-insoluble and alcohol-soluble, that combine with acids without the loss of a water molecule to form water-soluble hydrochlorides, hydrobromides, or the like, and that usually exhibit pharmacological action, as nicotine, morphine, or quinine.
- resembling an alkali; alkaline.
- any of a group of nitrogenous basic compounds found in plants, typically insoluble in water and physiologically active. Common examples are morphine, strychnine, quinine, nicotine, and caffeine
