From Longman Dictionary of Contemporary Englishcash cowˈcash cow noun [countable] PROFITsomething that a company sells very successfully and that brings in a lot of money
Examples from the Corpus
cash cow• The $8 billion video rental industry is the biggest cash cow ever developed in entertainment.From Longman Business Dictionarycash cowˈcash cow noun [countable]1FINANCE a very profitable business or part of a businessMail order should be seen as a cash cow that will generate cash for further moves into information services.GM and Ford have used luxury cars as cash cows; giving those up could have a terrible impact on profitability.2MARKETING in the GROWTH/SHARE MATRIX, a product with high market share in a low-growth market 