A political anarchist is one who believes that all forms of government are unnecessary and therefore rebels against authority and/or seeks to see it undermined/dismantled. And who further seeks to establish a society based on voluntary cooperation and free association of individuals and groups without coercion.
I would assume that an Anarchist Anabaptist would be someone who holds the same views with respect to religious institutions and who believes that organized hierarchical religion is unnecessary and that a society based on voluntary cooperation of Christians and free association is superior to the current smorgasbord of different organized groups and sects.
But I too would be interested in hearing what Chris means.