What is "ripred"

Ripred is an abnormally large rat and capable fighter who appears in Suzanne Collins' The Underland Chronicles. He is an important character in all five of the series' books. Ripred is what many people and animals in the Underland refer to as a "rager", or a natural born killer. Even though he is a rat, or a gnawer, as the Underlanders say, he often fights alongside the humans - frequently against other rats. Ripred is usually sarcastic, snide, and overbearing, but he has occasionally shown compassion and tenderness, especially with the main character's younger sister, Lizzie. The books describe him as being just as large as the other six-foot rats of the Underland, having a gray coat, and marked by a diagonal scar across his face.