(1) A condition that describes the complete shut down of traffic in the leftmost lanes of a multiple lane two-way street in which opposing lanes of traffic are separated by a median or neutral ground. In a Mexican Death Spiral, the first car car heading in one direction attempts to turn left across the median and comes to a stop to allow traffic to safely pass. Another car heading in the opposite direction also attempts to turn left across the same meridian and comes to a stop to allow traffic to safely pass. The death spiral is complete when additional cars stop behind the earlier stopped cars such that neither of the first cars can turn left because the path is now blocked by the subsequent stopped cars that have left no gap to cross.
(2) A situation that has come to an irreversible standstill, typically on internet message boards by two forum trolls clogging up the thread with their own tangential argument.
(1) Q: What took you so long to get here?
A: There was a Mexican Death Spiral at Carrollton Avenue that had traffic backed up for 10 minutes.
(2) Thanks PosterA and PosterB for causing yet another Mexican Death Spiral.