The most covered with cobwebs or most resembling cobwebs; superlative form of cobwebby.
From 'cobweb' plus superlative suffix '-est'. This is the highest degree form in the comparison chain (cobwebby → cobwebbier → cobwebbiest).
English speakers have been using superlatives like this for centuries to express extremes—the '-iest' ending became so powerful that we apply it even to compound words like 'cobweb,' showing how productive and flexible English word-building really is!
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