(1) A spurious bro who tries to fit in with genuine bros, but fails
(2) A poser, wannabe or social climber, often marked by overconfidence
Sometimes used by Anglo-Americans to express ethnic distaste or xenophobia, especially toward Italians, Jews, Eastern Europeans and even Irish
Also slang for jabroni
Bro 2: "I wish I knew. What kind of bro rocks an untucked black button down? And hair gel?!"
Bro 1: "A j bro, obviously. And chinstrap sideburns, to boot!"
a.k.a. "Jay", then "'bro", then " J-BRO", "j- b-dub" (jbw), " j-b dub-stylee" (when a sound engineer for ska / reggae band), and "jim-bo".
original response from said character in 1995, "dude, my name is Jim! ..... Uhh..., you know?... James?!
J- bro has been the contraction for at least one male who's name begins with a j and who's name doesn't match up with his face, causing confusion with more than one drunken musician in Boston, while auditioning guitarists in 1995.
" j-bro, when are YOU gonna buy some beers?"
"j-b-dub! doin' sound at t.t.'s tonight?"
"Iree!!! dub stylin' j-b-dub's in the house tonight!"
".. whatch you godda do is relax jim-bo!"