Definify.com
Webster 1913 Edition
Alkaloid
Al′ka-loid
(ăl′kȧ-loid)
, Noun.
(Chem.)
An organic base, especially one of a class of nitrogen-containing substances occurring ready formed in the tissues of plants and the bodies of animals.
☞ Alkaloids all contain nitrogen, carbon, and hydrogen, and many of them also contain oxygen. They include many of the active principles in plants; thus, morphine and narcotine are alkaloids found in opium.