"Packed audience" refers to a venue or space filled with a large crowd of people, meaning it is very full or crowded with spectators or attendees. Full definition
These easy yuks were delivered to a celebrity - packed audience in full and complete agreement — a Beverly Hilton ballroom clad entirely in black to show support for the «Time's Up» movement of actresses and others who have pledged to end discrimination and harassment in the workplace. (washingtonpost.com)
Strobes pulsed through fog as a tightly packed audience sought to get a shot of the DJ. (links2exchange.net)
The fairly packed audience started vocally reacting «Rocky Horror» - style to some of the more overtly melodramatic turns with «oohs,» «ahhs» and even laughter. (rogerebert.com)