I think being just dry means just coasting on a period of sobriety, without doing anything to maintain it throughout the future. Though I also do not use the term "dry drunk" ever.
My biggest problem with "dry drunk" is that it always suggests its opposite the "true AAers." AA does not need a class system, everyone is at a different point along the line, whenever you set yourself apart by debasing other people's recovery you do nothing but jeopardize your own (kissing your humility goodbye.)
Last time I saw a guy who once harshly accused me of being a "dry drunk" he was looking pretty rough after 60 days in rehab. I don't call it comeuppance, but it was definitely educational for me. You can be intense and hardcore about AA, but that doesn't mean your sobriety is in good shape. :\