Wikipedia
A big lie is a propaganda technique. The expression was coined by Adolf Hitler, when he dictated his 1925 book Mein Kampf, about the use of a lie so "colossal" that no one would believe that someone "could have the impudence to distort the truth so infamously." Hitler asserted the technique was used by Jews to unfairly blame Germany's loss in World War I on German Army officer Erich Ludendorff.
Usage examples of "big lie".
He was telling the big lie to save the Bands, a thing they could and would not do to save themselves.
If liberals applied half as much energy to some business endeavor as they do to creating the Big Lie, they would all be multimillionaires.
The Moloch story is what later ages would have called war propaganda, the big lie.
She'd told him a whopping big lie as soon a she'd entered the box.