Dictionary.net

The burnt smell and acrid taste, which volatile products-gaseous and liquid -contract, when animal or vegetable substances are decomposed by a strong heat. The cause of this smell is seated in an oil, called empyreumatic, which does not exist in the substance subjected to the operation, but is the result of its decomposition. If the empyreuma occurs when the organic substance is placed in a still with a liquid, it is owing to the solid matter touching the bottom of the vessel to which the fire is applied.

The process of burning or roasting; also the odor produced by heating an animal or vegetable substance. [Gr.]

n. [Greek] The peculiar smell and taste of animal or vegetable substances when burnt in close vessels, arising from an oil developed by the process of decomposition.