The group equivalent of being hit by a truck.
The team all go out for dinner, eat bad salmon mousse, and die. Also, any other reason for mass loss of developers. Not exactly common, but teams have been known to defect en masse, or you could just have bad luck and a number of people leave about the same time for different reasons.
So named from a skit in the MontyPython film TheMeaningOfLife, where a dinner party of British suburbanites is visited by Death.
And I thought it refers to what happens to salmon when they go through the turbines on the Columbia.See also TruckNumber, MoreFunWithTruckNumbers."Hey, I didn't even eat the mousse ..."