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(Law) an informer whose information implicates a large number of people in terrorist activities or other major crimes
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|Noun||1.||supergrass - a police informer who implicates many people|
Britain, Great Britain, U.K., UK, United Kingdom, United Kingdom of Great Britain and Northern Ireland - a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom