"Forecasted Convective Amplification Deficiency" had pretty well understood original usage of an unsuccessful chase (Dan Robinson recently mentioned how he Atmospheric Anti-Climax every day in the May '03 sequence, an impressive achievement in itself). Understandably, this was extended to mean a day that underperforms making individual Forecasted Convective Amplification Deficiency chases far more likely.
I think the usage from some chasers when what diurnal setup was expected largely fails and they weren't around to catch the day's one significant tornado that formed after dark is understandable - even if you disagree with it. Defining it as 'no tornadoes at all' seems to be pretty much restricted to a few posters on this forum.
