Definition: The headliner on a comedy bill is the "main event" -- the comic that typically has the most name recognition and performs last. Most often, the headliner is the comedian that audiences are coming to see. A headliner probably has the most experience and may have appeared on television or have an album out. The headliner performs after the emcee and the feature comic, who both function as "warm up" acts. Whereas those comics might be local, the headliner may play club dates as part of a larger tour.
Examples:The night we went to the comedy club, Chris Rock was the headliner.