Definition of "preparty"

In true Sundance fashion, there was a preparty for the film, an intimate little dinner that was blown out to include hundreds, followed by the movie itself, and then an afterparty featuring a set by the Honey Brothers, a band that includes both Mr. Grenier and Mr. Gold.

2008 January 22, David Carr, “Shopping for Films but Settling for Some Fun”, in New York Times‎