Inside joke between the most amazing couple in the world. They're anniversary is Febuary 14th, hence 214. And the word bad comes from the letters spelled out on a phone.
(2=B, 1=A, 4=D)
There are often words, such as hella, put inbetween 214 and BAD, to exaggerate how close and tight of a couple they are. In this word, Bad = amazingly perfect together.
Joseph: "Baby, i love you"
Victoria Beckingham: "Hun, i love you too. 214WEBAD!