Burp. Or 'blow bubbles', as the article put it. I am probably going to make a mess of the explanation provided within, but here's my best shot:
You might have heard of 'Hawking radiation'- kudos if you have- but for those who haven't, it's a principle by Stephen Hawking that a black hole doesn't necessarily keep all the matter it sucks in forever, but rather leaks out the odd particle here and there, which pops up just outside the event horizon. How that's supposed to work, don't ask me. He's Stephen Hawking and I'm not. Eventually- billions of years down the road, maybe trillions- if the black hole doesn't suck in anything else, it will one day evaporate due to lack of mass.
That established, the article has found a big mass of gamma-ray-emitting gas, shaped like a pair of bubbles, on either end of the black hole at the center of the Milky Way. Douglas Finkbinder of Harvard, leader of a team of people that found it, thinks it might have come when the black hole took in a lot of matter at once and, basically, burped. Or "expelled jets of material".
Really, just click the link. I'm afraid to venture any further attempts on this one.