The phrase usually means "highly compressed full version." Scammers exploit this by offering .exe files (Windows executables) disguised as ISOs. When you run them:
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This article is for educational and informational purposes only. Downloading copyrighted games without owning the original copy violates intellectual property laws. The author does not host or provide direct links to game ROMs or ISOs. Always support official releases. The phrase usually means "highly compressed full version