3 to 6 people sitting in one car parked in a commuter lot engaging in activities such as chain smoking, drinking, recreational drug use, listening to music, talking shit about people, and sometimes casual sex. Usually a last ditch effort to get fucked up without having a place to go and the bars are lame. Often frowned upon by the unitiated. Usually they last until the wee hours of the morning.
"Had nothing to do last night so we just sat at the commuter lot for a car party and listened to "Midnight City" by M83 on repeat and got blackout drunk."