When someone is raging, they're absolutely furious. The raging toddler having a temper tantrum in the supermarket might make you think twice about your new babysitting job.
The adjective raging describes anyone who is full of rage, an intense and sometimes violent kind of anger. The phrase "raging bull" is commonly used not only for an enraged bull that's about to charge, but also as a nickname for people and things with that kind of fury and ferocity. And if something is particularly forceful, it's also raging, like a raging thunderstorm or raging torrents of water during a terrible flood.