Expanded or widened, usually describing something that becomes larger or more open, like pupils in dim light.
From Latin 'dilatatus,' past participle of 'dilatare' (to spread out), combining 'dis-' (apart) and 'latus' (wide). Entered English in the 14th century through medical and anatomical terminology.
Your pupils dilate automatically in low light to let in more light, but they also dilate when you see something you're attracted to—ancient Romans noticed this and used it as a test of honesty in negotiations!
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