一问三不知,指如何问都不了解(say I dont know to every question),非常糊涂或非常无知。可以翻译为be entirely1 ignorant; not know a thing。与英文惯用语not know the time of day意思相近,表示to be completely unintelligent, daft, or not alert。
例句:
别问他了,他一直一问三不知。
Dont ask him any questions. He never knows the time of day.