A narrow notch or groove, as in the keyway of a lock; also, a slit or opening, such as the one in a door. A slot in a machine is where coins drop to make the device work. Someone who slots something into another object or into a space does so easily and without fuss. His car seat belt slotted into place easily.
The name “slot” was originally used for automatic vending machines but by the early 20th century had come to refer almost exclusively to gambling devices. The earliest machines were mere novelties—two toy horses that raced after a coin was inserted in the machine, for example—although by the 1880s some proprietors began to accept wagering money (usually in drinks or cigars) from customers and pay off winners by using trade tokens, often shaped like bars of gold or silver.
By the 1920s, the widespread popularity of slot machines prompted some states to ban them. However, a handful of manufacturers located in cities where the machines were legal, such as San Francisco, managed to stay in business until the city banned them in 1909.
Modern slot games are based on a variety of themes. Often they are themed after a famous historical event or period, such as the California gold rush of 1848 to 1855 or the Klondike gold rush 50 years later, in which thousands of prospectors flocked to search for their fortunes. Other themes are more abstract, such as space, ancient Egypt, or movies. Each game features a different set of symbols, but most include the classical card suits, numbers (7 is a popular one), and various pictured fruits.