A derivative of Heads up, this term was widely used(shouted) in the lot before and after Phish shows in order to alarm surrounding bystandards that law enforcement was in the vicinity and to conceal any contraband immediately. It was often used on shakedownwhen an undercover officer was discovered, or a regular officer was on the prowl and somewhat hidden by the general crowd. It was also seen on a popular fan made t-shirt which used a parody of the 7Up logo and read "6 Up, The Uncoola".
Head #1: "6 Up!"
Head #2: "Shit, stash those goo-balls and caps!"