Dictionary.net

From (com, and urere, ustum) " to burn." These terms have been applied to the extraordinary phenomenon of a rapid destruction of the human body, by being reduced to ashes either spontaneously or by the contact of an ignited substance. It is said to have occurred in the aged, and in those that were fat and hard drinkers. In such, Dr. Traill has found a considerable quantity of oil in the serum of the blood. Vicq dAzyr, Lair, and Dupuytren think it necessary, that the body should be placed in contact with an ignited substance. Le Cat, Kopp, and Marc are or opinion that this is not necessary. The former appears to be the more probable view.