combust

Etymology

From Middle English combust (“burnt”), from Old French combust, from Latin combustus, the perfect passive participle of Latin combūrere (“to burn up”).

verb

1. To burn; to catch fire.
   Brom swore after that he spoke only the truth, the truth that as he sat by my side praying for my soul, my body had combusted into flame, the fire rapidly engulfing my entire being. 2014, Adelais Selwyn, Eadric, volume 1
2. (intransitive, figurative) To erupt with enthusiasm or boisterousness.
   The audience combusts. 2012, Oliver Burkeman, The Antidote, Happiness for People who Can't Stand Positive Thinking

adj

1. (obsolete) Burnt.
2. (astrology) In close conjunction with the sun (so that its astrological influence is "burnt up"), sometimes specified to be within 8 degrees 30'.
   Guianerius had a patient could make Latin verses when the moon was combust, otherwise illiterate. , I.iii.1.3
   Who can discern those planets that are oft Combust, and those stars of brightest magnitude that rise and set with the Sun, untill the opposite motion of their orbs bring them to such a place in the firmament, where they may be seen evning or morning. 1644, John Milton, Areopagitica

noun

1. (obsolete) That which undergoes burning.