"Honey wagon" is a facetious traditional general term for "a wagon or truck for collecting and carrying excrement or manure", such as a cesspool emptier, which serves as a sanitation system including at campgrounds, and marinas. The operator connects a hose to the discharge outlet on the recreational vehicle, boat or building and pumps the waste into the wagon's tank. When the tank is full, the operator should empty the tank at an approved dump station or sewage lagoon. The more correct term is "vacuum truck".
Film and television industry
A honeywagon is a mobile toilet unit used in the film and television industry. The legend behind the name 'honeywagon' is thought to relate to the 'honey-colored' liquid that comes out of it when emptying the holding tanks. Many are the size of a semi-trailer. Some honeywagons will be just two large toilets. Others are a combination of variously sized rooms for specific purposes: these rooms can be private dressing rooms assigned to a single person, larger rooms configured for the wardrobe, or makeup departments, small individual toilets for the crew to share, and multiple user or individual shower rooms for bathing.
In the UK a honeywagon usually refers to a set of toilets used by the cast and crew. These come in all shapes and sizes - either trailer-base or built into the box body or a truck. In America, the term honeywagon is usually given to a truck, trailer or combination of both with a number of dressing rooms for the actor. These either have individual toilets or a communal set built in.
When Japan was occupied, the servicemen marvelled at the wagons that carried large barrels of feces from under the toilets in Japanese homes to be used as fertilizer in the rice paddies, and nicknamed them honey wagons as a sarcastic referral to the strong odor that trailed behind them.