four-wheel drive

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

• noun An automotive drive system in which mechanical power is transmitted from the drive shaft to all four wheels.

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

• noun A four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a transmission that provides power directly to all four wheels of a motor vehicle
• noun a motor vehicle with a four-wheel drive transmission system