British Slang: Those often irritating 'charity' representatives who approach you on the streets, encouraging you to provide credit card details for making monthly donations towards certain charities.
The 'chuggers' are trying to get you to quickly swallow the whole line they're pitching - hence 'Chugger.' Typically, the chuggers receive half of everything you agree to give and the company takes another 40 percent, leaving only ten percent for the real charity.
I've just been approached by more chuggers on the street corner. Today they're chugging for Save The Children!