A broke ass hippie
who will rush the gates of a concert with a large group of people in hopes of rushing by security and making it into the show. Only about 40% of a gate rushing crowd will actually make it into the show free, while the other 60% are either arrested or kicked out of the show. Sometimes hundreds of people will all rush the gates at once into the show, usually resulting in following shows on the tour getting cancelled.
Before Jerry died in '95, gate crashers had what would become one of the Grateful Deads last shows ever cancelled after they broke down the fence surrounding the concert, and hundreds of gate rushers made it by without getting caught.