DEFINITION of 'London Stock Exchange-LSE'. The primary stock exchange in the U.K. and the largest in Europe.Originated in 1773, the regional exchanges were merged in 1973 to form the Stock Exchange of Great Britain and Ireland, later renamed the London Stock Exchange (LSE).hat are the advantages and disadvantages of listing on the Nasdaq versus other stock ... The primary advantages for a company of listing on the Nasdaq exchange are lower listing fees and lower minimum requirements ...