That's code for an alligator that might be a threat.
Perhaps a better description is "tourist trained."
Gators know a free handout when they find one and thus, in areas were visitors are using food to attract them for a better view, they are commonly seen approaching to the sight of humans on the shore (or in a boat). They aren't being aggressive, they are just doing as they've been unwittingly taught.
The problem isn't the gators but rather tourists being a nuisance to themselves.