Just found this.
XREAS stands for "Cross Linked Relative Absorber System".
X-REAS was designed to help improve vehicle on-road handling performance. This technology links each of the vehicle's shocks to it's diagonal counterpart via a gas hydraulic chamber. During cornering or when traveling over bumpy surfaces, the gas hydrauilc chamber acts like a bank "borrowing" fluid from the cross-linked shock bearing the least amount of force and "loaning" it to the shock sustaining the greatest amount of force. This exchange of fluid helps the 4Runners wheels maintain contact with the driving surface and helps lessen vehicle body sway, pitch and roll, making for a more comfortable ride.