From Longman Dictionary of Contemporary Englishvertical expansionˌvertical exˈpansion noun [uncountable] technical when a company starts to do or make some of the things that used to be done or made by companies it did business with
Examples from the Corpus
vertical expansion• Finally, vertical expansion so that suppliers can be controlled may also be a short-run goal.• This increasing vertical expansion of the business also enabled the Ashleys to keep a much tighter control on their product's image.From Longman Business Dictionaryvertical expansionˌvertical exˈpansionCOMMERCE when a company starts to take on the business activities that are carried out by its suppliers or customersVertical expansion enabled the directors to keep much tighter control of the marketing strategy. → expansion 