This is not a common slang term. As was said, more context would be needed. Mostly due to Marvel Comic's X-Men, wolverines kind of got a bad rap as being one of the most feared animals. They can be aggressive, but not always.
So the term could mean "looking aggressive, like they might attack". However, many sports teams use a wolverine as their mascot, so it could possibly even mean "looking like a Wolverine sports fan".