The terminology is a mess. In an ideal world we'd be able to get everyone to sit down, say what they did and wore and thought and felt in nice short simple everyday words, and then having collected everyone's feelings and experiences we could come up with some terminology to fit that. But no, we have words with multiple meanings. It's a common problem...
There seem to be at least three meanings for "transgendered", for example. 1) people who identify wholly as female if XY, or wholly as male if XX, who live as their preferred gender 24/7 or who are thinking seriously about it or who would if circumstances permitted. 2) anyone who's anywhere on the "transgender spectrum", who cross-dresses (or similar) for any reason whatsoever. 3) people for whom cross-dressing is not (or not entirely) a sexual fetish or "I just like the clothes", but they don't necessarily want full full-time womanhood (or manhood, for FTMs), even if it was convenient for them. Possibly also people who don't crossdress but who have the feelings of not entirely identifying with their birth gender might fit in here.
I've seen "transgendered" to refer strictly to group 1, or to group 2 (of which 3 and 1 are subsets) or to group 3 (of which 1is a subset). There are also a variety of words that seem to be used for 3-but-not-1, "genderqueer", "androgyne", "bigendered". There are various things you can do with two genders - you can switch between the two, display both at once, tastefully blend them together or try to eliminate them completely, and this can go on in how you dress, what you do with your body or go on purely in your head, perhaps you might have a male and female persona which you switch between. Finding which of these fits which label is beyond me.
There's also genderf*k, which as far as I can tell seems to consist of displaying strong male cues and strong female cues (e.g. breasts and a beard) with the pretty much explicit intention of messing with people's heads.
So now it seems there are at least three uses of "just a crossdresser" - for people who are 2-but-not-1-or-3, for people who are 2-or-3-but-not-1, for people who are any of those three but aren't planning on hormones or SRS.
Getting people to stick to one definition of "transgender" or "crossdresser" or "only a crossdresser" seems nigh-on-impossible to me, too many people have invested too much in their labels, there isn't an authority that's going to be credible with everyone, it's just a non-starter.
Now someone will do doubt point out that my 1, 2 and 3 are just as much of a mess as the old terminology, and I won't argue with them. I just made those numbers up to make a point.
Me? I like to think there's something feminine (when I'm feeling brave, female) about me, and crossdressing is an expression of that, rather than just a desire for pretty clothes or a sexual thing. The feminine came first, the CDing later. But I don't CD all that often, I feel rather more male than female (when I'm feeling hard-headed, 100% male, although not particularly masculine), and I'm still exploring what all of this means to me and what my true feelings are. Whether that makes me transgendered or not, "a crossdresser only" or not... you can answer that for yourself, I've caused myself too much angst in the past trying to answer those questions, so I'd rather not worry about those things.