Originally, a fan or follower of the Philadelphia-based professional sports teams who refused to celebrate the two Stanley Cup championships won by the Philadelphia Flyers in 1974 and 1975 on the grounds that hockey should not be considered a "major" sport; today, a Philadelphia sports fan who is either unduly pessimistic about one or more of the local teams' immediate prospects, or one who strenuously disagrees with the policies, player-personnel decisions etc., made by said team or teams.
Many sports fans in Philadelphia regard the local sports-talk radio station, WIP, as nothing more than a vast sounding board for Negadelphians.
by Anthony Brancato August 18, 2005
The manner is which Philadelphia sports fans act towards their teams at the onset of the slightest hint of a supported teams situation worsening, wether it be short or long term. (Expect the worst, hope for the best)
Billy is watching the Eagles play the Cowboys. The eagles go ahead 20-0 but the kicker misses the extra point. Billy immediately calls his cousin to trash the team without positive mention of the 20 points.
OR
A star player after a few good years is struggling. Billy immediately calls the radio station and screams for his benching and removal.
In Philadelphia, these are acts of a negadelphian.
by Swaggyobservationalist December 7, 2020