Slang's the use of highly informal words and expressions that aren't considered standard in the speaker's dialect or language. Defining slang Few linguists have endeavored to clearly define what constitutes slang. Attempting to remedy this, Bethany K. Dumas and Jonathan Lighter argue that an expression should be considered "true slang" if it meets at least two of the following criteria: It lowers, if temporarily, "the dignity of formal or serious speech or writing"; in other words, it's likel… (More on Slang)