instant messaging
From Longman Dictionary of Contemporary Englishinstant messagingˌinstant ˈmessaging noun [uncountable] a type of service available on the Internet that allows you to quickly exchange written messages with people that you know instant messaging services —instant message noun [countable]From Longman Business Dictionaryinstant messagingˌinstant ˈmessaging abbreviation IM noun [uncountable]COMPUTING a type of service available on the Internet that allows you to quickly exchange written messages with people you know