car wash

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

• noun A place or business equipped for washing cars and other motor vehicles.
• noun The act or an instance of washing a car, especially at a car wash.

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

• noun An event at which people (often children) wash cars, often for a small fee or donation
• noun A place at which a car is washed, usually for a fee and often mechanically by driving the car through a tunnel.
• noun An instance of washing a car, especially such a place.