The phrase "after dark" refers to the time of day when it is dark outside, typically after sunset and before sunrise. It is often used in reference to activities or events that take place during the nighttime, such as nightlife entertainment, parties, or outdoor gatherings.
For example, someone might say "Let's go out after dark and explore the city" or "The after-dark scene in this town is amazing." In these contexts, "after dark" suggests a specific time period and the activities associated with it.