To make noisy or to cover with clattering sounds.
From be- prefix plus clatter, which comes from Middle English clateren, an imitative word imitating the sound of repeated sharp metallic noises. The be- prefix adds the sense of 'to make' or 'to cover with' to the base word.
Onomatopoeia—words that imitate sounds—are some of the most fun in any language, and clatter is a perfect example: it literally sounds like what it means! English has hundreds of sound-imitation words (bang, hiss, fizz, splash), many more than languages like French or German, possibly because English picked up lots of them from other languages during its long history of invasions.
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