The Jump Guardian is a boss in the GameCube video game Metroid Prime 2: Echoes. It is the second of many guardians that Samus Aran must fight. Once she defeats the Jump Guardian, she'll obtain the Space Jump Boots, which essentially allows her to perform a double jump.
The guardian is a Warrior Ing that can, via the Space Jump Boots, leap distances that it could otherwise not. Often times it'll generate a force field, though it won't be able to keep it up forever.
Once you shoot it with multiple missile shots or charged beams, it'll eventually die, allowing you to get the Space Jump Boots.