In a manner that is capable of being dilated or expanded; with the ability to stretch or enlarge.
From dilatable + -ly (adverbial suffix). Creates an adverb from the adjective dilatable through standard English word formation. Extremely rare in actual usage.
This is one of those wonderfully archaic adverbs you almost never see—it would mean 'in an expandable manner,' but modern English just says 'with the ability to expand' instead.
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