What is "cried wolf"

Usage examples of "cried wolf".

Because of his propensity for telling whoppers in even the most trying times, he was now like the little boy who cried wolf--Ake was resisting the truth because it was coming from him.

My gut told me that the woman in the car had been following me, but then again, my instincts had cried wolf before.

My gut told me that the woman in the car had been following me, but then again, my instincts had, er, cried wolf before.