Burned or scorched; appearing darkened or gloomy as if by heat.
From Latin 'adustus,' past participle of 'adurere' meaning 'burned.' It entered English in the 14th century with both literal and metaphorical meanings.
Shakespeare used 'adust' to describe melancholy and dark moods—medieval medicine believed that burned or overly-heated bile caused depression, so 'adust' described both scorched skin and a scorched temperament.
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