I get that big time from playing FPS games. In that case it's complete lack-of-motion sickness. Body is completely stationary while eyes and ears say the complete opposite.
I cannot read in a car or on a bus due to motion sickness (yet I can on a train or plane as those modes of transport go essentially in a straight line and don't throw my body about). So as long as my body isn't being thrown around at odds to input from eyes and ears my brain doesn't question anything.
F 5 ft 3. HW: 196 lbs. Primal SW (May 2011): 182 lbs (42% BF)... W June '12: 160 lbs (29% BF) (UK size 12, US size 8). GW: ~24% BF - have ditched the scales til I fit into a pair of UK size 10 bootcut jeans. Currently aligning towards 'The Perfect Health Diet' having swapped some fat for potatoes.