expression, godan verb (-bu)
be fired; be decapitated
Idiomatic expression literally meaning 'the hat stand flies off'. Historically referred to beheading, but in modern usage it almost exclusively means losing one's job. The decapitation sense is archaic and rarely encountered outside historical contexts.
あの社員は遅刻が多くて、ついに笠の台が飛んだらしい。
That employee was often late, and apparently finally got fired.
昔の武士は戦で負けると笠の台が飛ぶこともあった。
In the old days, a samurai could lose his head if he lost a battle.