A basic definition: an injury resulting from a quick jerk of the neck.
A more technical definition: a spinal injury effecting the muscles in any number of regions of the spine from the coccyx to the cervical vertebrae, most frequently the latter. Trauma to the muscles surrounding the spine results in a build-up of scar tissue within the fibres of the muscles, giving rise to the 'trigger-point' effect, where discomfort or swelling in an effected area can result in a propagation of pain to other connected regions.
nah, I've had it mountain biking though. Not skiing. Couple of my mates have had it from a car but I don't know anyone who's had a bad injury from it, just sore for a day or so.
I got whiplash riding the bus home one time. Some idiot pulled out and we had to stop real fast and the school gave my family 100 bucks because of what happened to me. hehe