A person who jacks or steals someone else's swagger. When someone that is not very cool takes feels the need to take someone else's swagger or awesomeness to try and make themselves cooler.
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-jackin me, you will never be as awesome or cool as me.
Abbey: Agreed! Raul is soooo cool!