Final answer:
You overheard an example of colloquial language or slang at the DART station, which is typical within informal speech communities.
Step-by-step explanation:
If you overheard the following interchange of communication at the DART station "Hey, man, what did you do on the 4OJ?" then you overheard an example of colloquial language or slang within a particular speech community. When people are in informal settings, they often use language that is specific to their cultural or social group, which can include slang terms, jargon, or a style of speaking that may not be understood outside of that context. The effectiveness of such overheard communication has also been studied in terms of persuasion, according to Walster and Festinger (1962).