Able to catch fire and burn easily; also used to describe a situation or person that is volatile or easily angered.
From Latin 'combustus,' past participle of 'comburere' meaning to burn up completely. 'Com-' means together and 'burere' means to burn, literally 'burn together.'
The word became really popular metaphorically in the 1960s during the civil rights era—people described tense situations as 'combustible,' meaning they could explode into violence at any moment. It's one of those words that started scientific and became psychological.
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