The "portable" version of 9xflix might refer to a lightweight version of the site that loads quickly on 2G networks or a modded APK (Android application) that doesn't consume battery or RAM. Some third-party developers create "portable" versions of piracy sites that can be run from a USB stick without leaving browser history.
The word "portable" is the most ambiguous yet crucial part of the keyword. It does refer to a physical device. Instead, in file-sharing jargon, "portable" usually means: 9xflix 300mb portable