sway bar

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A metal bar connecting the left and right suspension systems at the front or rear of an automobile or a truck, used to stabilize the chassis against sway.

from the GNU version of the Collaborative International Dictionary of English.

• A bar attached to the hounds, in the rear of the front axle, so as to slide on the reach as the axle is swung in turning the vehicle.
• Either of the two bars used on couplong the oront ano rear sleds of a logging sled; also, the bar used to couple two logging cars.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An anti-sway bar.