Pile On Meaning

(transitive, idiomatic) to jump on top of someone or something quickly.

Example: 2006, Steven M. Hallock, Editorial and Opinion: The Dwindling Marketplace of Ideas in Today's News, Praeger, ISBN 978-0275993306, page 69:
  As football linebackers pile on a quarterback in a blitz, the newspaper editorialist heaped sarcasm onto the president.
2009, Human Kinetics with Thomas Hanlon, The Sports Rules Book - 3rd Edition, Human Kinetics, ISBN 978-0736076326, page 116:
  Piling on: Players may not pile on a runner after the ball is dead or intentionally fall upon any prostrate player.
2011, Michael Harston, The Show: The Michael Thomas Story, Xlibris, ISBN 978-1456862220, page 21:
  The quarterback turns and hands the ball to his fullback just as Sumo hits him in the backfield causing a fumble. Ball loose, ball loose screamed Jones. There is a mad scramble for the loose ball as bodies pile on top of each other.