Well, as much as I do not believe that etymology is destiny, I can't quite forget that "radical" comes from a word for "root," so I suppose that by "radical feminist" I mean a feminism which looks to the intolerance found in the deepest structures which are the most foundational--language, myth, logic, cognition itself--and tries to deal with it there, as opposed to liberal feminism which tries to deal with problems (mere symptoms of a greater disease?) on the surface, e.g. by passing laws (with various degrees of success).