look up any word, like swag:
 
1.
Used to announce the start of a battle, fight or competition. Similar to “let’s get it on” or "let’s get ready to rumble."
Wilmer Valderama always starts each Yo Mama competition by saying "let's bully!"

Example #2

FIRST IDIOT: You want a piece of me?
SECOND IDIOT: Maybe I do.
FIRST IDIOT: Let’s bully!
by HuskyMiller January 16, 2007