This Internet Slang page is designed to explain what the meaning of OSS is. The slang word / acronym / abbreviation OSS means . Internet Slang. A list of. Acronym, Definition. OSS, Office of Strategic Services. OSS, Open Source Software. OSS, Open Sound System (Unix digital audio architecture). OSS, Operations. 34 definitions of OSS. Definition of OSS in Military and Government. What does OSS stand for?.