Australian slang term for men's tight-fitting Speedo-style swimwear. The 'lump in the front' apparently resembles a budgie when it is stuffed down the front of someone's shorts. Ah, those crazy Aussies!!
In discussing his film "Revolver" on BBC's Radio 5Live, Guy Ritchie said that Ray Liotta's 'Mr. Macha' character, who parades around wearing only budgie smugglers for much of the film - was 'an impressive sight'.