In a blotchy manner; with blotches or in an uneven, spotted way.
From blotchy (adjective meaning having blotches) plus -ly adverbial suffix, creating an adverb that describes how something appears or is done.
Adverbs like blotchily are tricky because they describe qualities we can see, not actions we do—you can't really 'blotchily do something,' but you can paint or stain something blotchily.
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