A fish that translates any spoken language into a language that the person possessing the fish can understand.
To understand the Vogons, you'll have to have a babble fish in your ear. (For those who think this should be spelled babelfish or babel fish or BabelFish or Babel Fish - guti. Douglas Adams (who died May 11, 2001) would probably have appreciated the whimsy of randomly using alternative spellings.)
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