One of the world's biggest myths. The term is used to describe aggression, as seen from users of anabolic steroids. Usage of the term originates from (and now perpetuates) the myth that steroids make people aggressive.
In reality, increased testosterone improves mood, cognitive function, confidence, libido, and has many other positive effects as well. Some users have claimed, however, that they bring out who you really are. So if you're a dick with emotional problems, steroids will not fix your problems but just give you the balls to be an even bigger dick.
Many users of AAS are chicken-legged douchebags who have no business taking them to begin with. They end up killing themselves by doing stacks no intelligent bodybuilder would ever use, and using them 365 days a year.
A real phenomenon is when an AAS user completes their cycle. At this point, their body has not produced its own testosterone for a while, and they suffer a drastic decrease in T-levels. This LACK of testosterone can cause irritability and depression for a few weeks while the body struggles to play catch-up. But this is not caused directly by anabolic steroids (which testosterone is), but rather the lack of them.
Chris Benoit went roid rage and killed his family and himself. But as it turns out, the guy was just a complete dick with serious emotional problems.