Something that forms clumps, or a person or thing that clumps or walks heavily and noisily.
From clump + -er (agent noun suffix from Old English). This describes either something with clumping characteristics or something that produces clumps.
The -er suffix is endlessly productive in English—we can add it to almost any verb to create someone or something that does that action, which is why English never runs out of new words for people and things.
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