That is the pack's name for a selfish rider sitting at the back who doesn't do his or her share of the work.

BBC: England

Since that time, we've passed a Recovery Act that's put a middle-class tax cut into people's pockets, that has invested in infrastructure all across this country and put people back to work, and something that isn't noted often enough, has helped stabilize state budgets at a time in which we could have seen hundreds of thousands of layoffs in teachers and police officers and firefighters.

WHITEHOUSE: President Obama Speaks to Press After Cabinet Meeting