OSS/BSS, in telecommunications, stands for operations support system/business support system. The two systems, operated together by telecommunications service providers, are used to support a range of telecommunication services.
Previously OSS and BSS were more clearly separate entities but the term OSS/BSS (or occasionally BSS/OSS) has been in use since at least 2008  . The interface, for example, between the BSS capturing an order and the OSS fulfilling it could be quite simple.
Now, with more complicated and differentiated products and services being offered much closer liaison between the two is required, for example processing an order may require information on the services the customer already has, the network they are using, and currently available resources.
Use in VoIP and Unified Communications
Service providers in this area have even more requirements for an integrated OSS/BSS system. Examples include eCommerce, self-management, real time reporting, fraud prevention...
- http://www.ossline.com/2010/12/definition-oss-bss.html OSSLine: The Definition of OSS/BSS. Dec 2010
- http://www.ericsson.com/thecompany/events/oss-bss_957590547_c Ericsson at OSS-BSS World Summit, London, 2010
4. TCPaaS is an OSS/BSS platform that provides Service Providers white-label software that enables more self service functionality in an integrated operations and billing system.