A person who jacks or steals someone else'sswagger. When someone that is not very cool takes feels the need to take someone else's swagger or awesomeness.
Example: Raul: Oh my god I'm so awesome! And i think I'll take the Spanish name Cristobal!
Josh: Oh my god that Raul kid is sooooo awesome and cool! The only way I can be as cool as him is to Swagger Jack him and take the name Raul.
Raul: Stop Swagger Jacking me, you will never be as awesome or cool as me.
Example: Fishy: "i am defo Jack Swaggered"
Other person: "No you are blates drunk mate"
Fishy: "yeah. So i am Jack Swaggered 2K9"
Other person: "you are a drunken bellsniff mate"