noun

• (politics, history, chiefly US, offensive) A migrant from the Northern to the Southern States after the American Civil War of 1861–5, especially one who went South to gain political influence.
  "“You are way behind the times,” he said. “There is no Klan in Atlanta now. Probably not in Georgia. You’ve been listening to the Klan outrage stories of your Scallawag and Carpetbagger friends.”"
• (derogatory, by extension) One who comes to a place or organisation with which they have no previous connection with the sole or primary aim of personal gain, especially political or financial gain.
  "By the tenth century, out of the diversity of these Christianized Anglo-Saxon kingdoms emerged one of the most coherent political units in Europe, a single monarchy of England, with a precociously centralized government which eventually fell like a ripe plum into the grateful hands of Norman carpetbaggers in 1066."