-bust, -ust, -bur; bust-, bur-, ur- +
(Latin: burere, "to burn up"; from urere, with an inserted or faulty separation of b in amburere, "to burn around"; which stands for amb-urere, "to burn around", but it was misdivided into am-burere and because of this misdivision, the new verb burere was formed with the past participle bustum; so, it really came from urere, "to burn, to singe")
Adust came from Latin adustus, the past participle of adurere, "to set fire to; a verb formed from the Latin prefix ad-, "to, a direction toward" and the verb urere, "to burn".
It entered the English language in the early 15th century as a medical term related to the four bodily humors: black bile, blood, phlegm, and yellow bile; all of which were believed at the time to determine a person's health and temperament.
Adust was used to describe a condition of the humors in which they supposedly became heated or combusted. Adust (heated) black bile in particular was believed to be a source of melancholy (a tendency to be gloomy and depressed).
2. In surgery, cauterization.
2. Filled with glum or melancholy.
3. In medicine, having much heat in the constitution and little serum in the blood; therefore, gloomy; sallow (having a pale, sickly color or tinged with yellow; as, a sallow skin).
2. Etymology: from Latin comburere, "to burn up, to consume".
2. A chemical change; especially, oxidation, accompanied by the production of heat and light.
3. Violent anger or agitation: "Combustion within the populace slowly built up to the point of revolution."
4. Burning; consumption by fire; the development of light and heat from the chemical combination of a substance with oxygen.
5. Etymology: from Latin combustus, past participle of comburere, "to burn up"; from urere "to burn".
Combustion includes thermal, hydrodynamic, and chemical processes. It starts with the mixing of fuel and an oxidant, and sometimes in the presence of other species or catalyst.
The combustion products include heat, light, chemical species, pollutants, mechanical work, and plasma.
Cross references of word groups that are related, directly, indirectly, or partly to: "fire, burn, glow, or ashes": ars-, ard-; cand-, cend-; caust-, caut-; crema-; ciner-; ether-; flagr-; flam-; focus, foci-; fulg-; gehenna-; ign-; phleg-; phlog-; pyreto-, -pyrexia; pyr-; spod- (ashes; waste); volcan-.