before somebody can say Jack Robinson
(faster|quicker) than {sb} (can|could) say Jack Robinsonbefore somebody can say jack robinson
01
so suddenly or quickly that leaves one with no time to react or notice anything
Humorous
Idiom
Informal
例
They react to changes before you can say Jack Robinson, adapting instantly to new circumstances.
He finished the race before you could say Jack Robinson, crossing the finish line in a flash.
