jackjohn 

Someone who's given birth name is John but goes by Jack

Did you know his name is actually John?
Yeah, he's a total jackjohn

jackjohn by Xx_Jackjohn_xX June 23, 2017

jack/john 

A person who has the qualities of a Jack, and was given the birthname john. a jack/john has the sexiest eyes, and if you make him mad, he will destroy you verbally. he is amazingly smart and is truly the shit

OMG, he is so Jack/John

jack/john by JACKLOPEEEE May 7, 2018