green lightning: n. [IBM]
1. Apparently random flashing streaks on the face of 3278-9
terminals while a new symbol set is being downloaded. This hardware bug
was left deliberately unfixed, as some genius within IBM suggested it would
let the user know that ‘something is happening’. That, it
certainly does. Later microprocessor-driven IBM color graphics displays
were actually programmed to produce green lightning!
2. [proposed] Any bug perverted into an alleged feature by adroit
rationalization or marketing. “Motorola calls the CISC cruft in the
88000 architecture ‘compatibility logic’, but I call it green
lightning”. See also feature (sense
6).