Short in penis, long of himself. An ironic and savage diss used to describe high earning, arrogant stockbrokers and traders who think they are cool and clever because they describe everything in terms of trading positions i.e. long and short. These douchebags are oblivious to the fact that everyone hates them, including colleagues who are forced to pander to them only because they make a lot of money for the company.
Generic Wanker Banker: 'Hey baby, I'm massively long your fine ass.'
Betty: 'Doris I think that guy is trying to chat you up.'
Doris: Yeh I'm choosing to ignore him, he's gross and siploh asf.