In the context of 3DS emulation and fan translation, a "Repack" typically refers to a specific version of the patched game file (usually a .3ds or .cia file). The term implies that the translation patch has been "repacked" into the original game data, creating a standalone version that is ready to play without requiring the user to manually patch files.
Since a complete repack does not exist, most players use these methods: cardfight vanguard 3ds english patch repack