The universe is, to the best of my knowledge, a huge dynamic system. It is not random, as such; everything is shaped through action and reaction. But it is much too complex and large a system to accurately predict anything.
In mythology, Chaos is the void from which the world was born.
In common language, chaos refers to a great disorder.
In science, well, I don't pretend to understand anything about chaos theory, but, as Wikipedia puts it, it 'studies the behavior of dynamical systems that are highly sensitive to initial conditions'. Common applications are natural systems, like weather patterns.
When I imagine Chaos (capital 'C') as a supreme cosmic force or entity, it is most likely as a combination of all the various meanings of the word. It is the very nature of the universe. While seemingly random, it does follow strict patterns (call them the laws of physics, or whatever you will), but is, on the other hand, utterly unpredictable.
Chaos is impossible to personify, although aspects of it might be represented by avatars, like Eris (or, if you think about it, almost any deity, I guess). If I try to visualise it, I usually try to visualise a 'cosmos', with endless space, revolving planets, etc. Of course this doesn't really do it justice.