DW is when your front suspension components get worn or damaged and end up with a little bit of play in them causing normal road vibration to increase in frequency and intensity.
in short, your worst F'n nightmare lol.
should you ever experience it, it is in fact unmistakable. you're first thought might be something like, "holy $hi#, im gonna die." as the jeep feels like its going to shake itself into another dimension.
do a youtube search and you can see some videos to get an idea.
'95 ZJ: 5.2 v8 / 231 Tcase / 46RH