Definition of piling on:
(n) :
The process by which multiple people pick on, complain about or list the faults of their target.
(n) :
The steady addition of more problems to an already problematic situation or circumstance.
(n) :
The process by which additional combatants join an ongoing fight or argument when they think they know who will win so that they will be on the winning side.
(n) :
A fighting tactic wherein multiple people attack another.
(n) :
(by extension) An ongoing increase in a change or phenomenon, such as the popularity of a fad.
(n) :
(American football) An illegal strategy wherein players tackle an opposing player.