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Stock Exchange Automated Quotation System
An electronic system for trading mid-cap securities over-the-counter. Only securities traded on the London Stock Exchange but not included in the FTSE 100 can be traded on SEAQ. Its rules are considered rather stringent, and critics contend that this contributes to illiquidity on SEAQ. Because of its basic structure as an electronic, over-the-counter exchange, it is sometimes called London's NASDAQ.