I always liked the term 'Business Objects' - but that has always been co-opted by a company (SAP).
So hard to invent catchy new terms... Trying here but they all sound like business buzzwords...
Business Proxy, Business Delegate, Business Front, Business Agent, Company Blackbox, Business Interface, Company Platform, Company Rube Goldberg, Company Socket, Partner Interface?
Because I get annoyed every time someone uses "APIs" to make general statements while assuming that specific narrow meaning.