A slang dictionary is a reference book containing an alphabetical list of slang, vernacular vocabulary not generally acceptable in formal usage, usually including information given for each word, including meaning, pronunciation, and etymology. It can provide definitions on a range of slang from more mundane terms (like "rain check" or "bob and weave") to obscure sexual practices. Such works also can include words and phrases arising from different dialects and argots, which may or may not have passed into more common usage. They can also track the changing meaning of the terms over time and space, as they migrate and mutate. This makes them of interest to a variety of people, from oral historians, to etymologists, to the casual browser.