Crying wolf means to act like you are in danger if you really aren't, or in a broader sense, just to tell a lie to get attention. It comes from the fable of the little boy who cried wolf, about a boy who watched sheep, and he would yell that there was a wolf to get people to come rescue him, when there really was no wolf, he just wanted attention and to play a joke on people. He did it so often that over time they stopped believing him, until one day a wolf really did come and he cried "Wolf!" and nobody believed him so nobody came, and all the sheep (and maybe the boy too!) were eaten by the wolf. Basically it is an admonishment not to lie, or else people will not believe you when you tell the truth.

In reference to this tale, the phrase to "cry wolf" has long been a common idiom in English, described in Brewer's Dictionary of Phrase and Fable, and modern English dictionaries.The phrase "boy who cried wolf" has also become somewhat of a figure of speech, meaning that one is calling for help when he or she does not really need it. Also in common English there goes the saying: "Never cry wolf" to say that you never should lie, as in the above phrases. Source: Wikipedia to warn of danger that is not there The man is always crying wolf and now nobody believes him.

'To cry wolf' means 'to call for help when you do not need it'. If you cry wolf, people won't believe you when you really need help!

The real story about The Boy Who Cried Wolf: www.oglaf.com/wolf/

Cry wolf Meaning: To intentionally give a false alarm. Example: "Stop crying wolf, or else no one will come to your help in case of need."(http://www.buzzle.com/articles/idioms-and-their-meanings.html) Cry wolf To ask for help when you don’t really need it. “The old man phoned the police six times and asked them to come and see if there was someone in his house. Of course, the police never found anyone. Finally, the old man really did need the police, but they never came because they thought he was crying wolf.”(http://www.hotenglishmagazine.com/pdfs/HOT_ENGLISH/hot03.pdf)