From Longman Dictionary of Contemporary Englishupsizeup‧size /ˈʌpsaɪz/ verb [intransitive, transitive] to become larger in size, amount etc, or to make something do this Do you want me to upsize your fries?→ See Verb tableFrom Longman Business Dictionaryupsizeup‧size /ˈʌpsaɪz/ verb [intransitive, transitive]1computing to start to use a bigger computer system than beforeThe company hopes to sell to those businesses that are upsizing their applications.2human resources to increase the size of a company by employing more peopleThe Chief Executive said that it was an upsizing merger that would help the business grow.→ See Verb table