The Collaborative International Dictionary of English v.0.48:

carsick \car"sick`\ (k[aum]r"s[i^]k`), adj.
   feeling nauseous due to the movement of a car or other land
   vehicle; -- similar to airsick and seasick.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

carsick
    adj 1: experiencing motion sickness [syn: airsick, air sick,
           carsick, seasick]