It's a phrase that's come up again and again this week: in "Flash Boys," Michael Lewis' new book about high-frequency trading; in today's spirited debate on CNBC between BATS Global Markets President William O'Brien and IEX's Brad Katsuyama; and in almost every high-speed trading article in between.

Front running. But what the heck does it mean?

On Tuesday, I described it as a dog running off with your sausages, but that's not entirely accurate. It's more like the dog finding out how much you are prepared to pay for your sausages, buying up all the sausages itself and then selling them to you for a higher price.

Front running is when a high-frequency trading firm sees you bid a certain price for a stock in one exchange, and then uses its superspeed to get in front of you (hence, front running) in all the other exchanges, buying the stock that you want and then selling it to you for more than you originally bid.

Traders hate being front-run. Not just because it means they are paying more than they thought they would have to pay (heck, the client can eat the loss), but because they like to think of themselves as Masters of the Universe, people who dominate, who control everything around them. But if you're being front run, then you're in control of precisely nothing. You are, in fact, being led by the nose. Like a Master of the Universe's pack mule.

Yes, if you get front run, you're a donkey.

No wonder there's so much hate for HFT firms. Michael Lewis points out that the losers in the hedge fund game are often hedge funds, who trade on behalf of pension funds. Hedge funds don't like to be victims. And they sure as heck hate being seen as donkeys.

About the author

Paddy Hirsch is a Senior Editor at Marketplace and the creator and host of the Marketplace Whiteboard. Follow Paddy on Twitter @paddyhirsch and on facebook at www.facebook.com/paddyhirsch101