Most dusky; the darkest or most shadowy; most dim or most approaching the color and feeling of dusk.
From 'dusky' plus the superlative suffix '-est,' following standard English patterns for the highest degree of an adjective (like 'dark,' 'darkest').
The superlative 'duskiest' is rarely used today, but it appears beautifully in 19th-century literature to describe the deepest twilight or the most mysterious shadows—it's wonderfully precise for something we'd now just call 'very dark.'
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