Wiktionary
n. A box used to provide a soiling area for (usually) pet cats, generally filled with sand, clay chips, etc.
Wikipedia
A litter box, sometimes called a sandbox, litter tray, litter pan, or catbox, is an indoor feces and urine collection box for cats (as well as rabbits, ferrets, micro pigs small dogs such as Beagles and Chihuahuas, and other pets that instinctively or through training will make use of such a repository) that are permitted free roam of a home but who cannot or do not always go outside to relieve themselves. Many owners of these animals prefer not to let them roam outside for fear that they might succumb to outdoor dangers, such as weather, wildlife or traffic (it has been claimed indoor cats live, on average, ten years longer than outdoor cats). A litter box makes it possible to shelter pets from these risks.
In the wild, cats naturally excrete in soft or sandy soil for easy burial. They use their paws in a backward sweeping motion to cover their feces. To stimulate this instinctive desire, a litter box's bottom is filled typically with an inch (2.5 cm) or more of cat litter. Litter box filler is a loose, granular material that absorbs moisture and odors such as ammonia. Some litter brands contain baking soda to absorb such odors. The litter material also satisfies a cat's instinctive desire to use an easily dug material. The most common material is clay, although recycled paper "pellets" and silica-based "crystal" variants are also used. Sometimes, when an owner wishes to stimulate the cat's natural instincts, natural dirt is used.
Usage examples of "litter box".
Hamilton lifted himself up and reached for his crutches that leaned over by a pile of boots and a kitty litter box in the corner.
Dean looked around for help, but the sounds of vigorous excavation from the bathroom suggested Austin was in the litter box.
Under Anna's supervision it was converted into a litter box and food and warm milk set out to make the kittens feel at home.
Then Norman did his duty in the litter box and needed a kibble reinforcement.
She should have done something about a litter box, or made certain Lucifer was outside.
He was still hiding in the covered litter box, but he peeked out when he heard her voice.
So it wouldn't be any big deal for him to be without his litter box for a night.