From Longman Dictionary of Contemporary Englishday tradingˈday ˌtrading noun [uncountable] the activity of using a computer to buy and sell shares on the Internet, often buying and selling very quickly to make a profit out of small price changes —day trader noun [countable]From Longman Business Dictionaryday tradingˌday ˈtrading FINANCEwhen people buy and sell shares quickly using the Internet, which allows them to take advantage of small price changes → trading