AMERICAN STOCK EXCHANGE: One of three national stock markets in the United States (see National Association of Securities Dealers and New York Stock Exchange) that trade ownership shares in corporations. In terms of daily stock transactions and the number of stocks listed, the American Stock Exchange is the smallest of these three. However, it's composite index of stock prices -- AMEX is considered important enough to be flashed briefly on the nightly news. See also | stock market | corporate stock | National Association of Securities Dealers | New York Stock Exchange | Dow Jones averages | Securities and Exchange Commission |