To burn or undergo combustion; to catch fire or ignite.
From Latin 'combustus,' the past participle of 'comburere' (to burn completely), combining 'com-' (together/thoroughly) and 'urere' (to burn). The word entered English medical terminology before general use.
In astrology, a planet is 'combust' when it's too close to the sun to be seen—literally burned by solar light. Medieval astronomers borrowed this word from chemistry to describe celestial obscuration, showing how scientific language spreads across disciplines.
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