A Jeff box is one who is always playing video games. He never leaves the house without his Xbox. He typically never showers and is one to leave the room while you can still smell him. He is the one that is always third wheeling and never gets the hint to leave you two alone. A Jeff box is the one who is most definitely gay but when confronted he becomes angry and tries to divert the attention to someone else.
Dude take you and you Xbox and leave me and my girlfriend alone. Take a shower too because your being a real Jeff box.