dogpile

Short definition from Wiktionary

Noun

1. 1
   A disorderly pile of people formed by jumping upon a victim.
2. 2
   Any similarly disorderly pile of people or things.
3. 3
   A pile of dogshit.
4. 4
   The situation where many participants attack the same user (on a discussion forum or similar).
5. 5
   A cache stampede.

Verb

1. 1
   To jump into a dogpile.
2. 2
   To pile on, to overwhelm in other senses.
3. 3
   For many participants to attack the same user (on a discussion forum or similar).