What does 'blow the whistle' mean?

If I know someone is using the company account on personal pleasures and I wrote a letter to the his boss about his conduct, then I blew the whistle on him.

Huh??

Hi WA

The expression 'blow the whistle (on somebody/something)' is not slang. It's an idiom. It is somewhat informal, though, so I wouldn't use it in an extremely formal text.

Hi Goodman,

I'm curious about the tense switch in your sentence. Could you please explain why you switched from the present tense to the past tense within a sentence?

If I were to make it hypothetical (Type 2 conditional), I would write as follows:

If I knew someone is using the company account on personal pleasures and I wrote a letter to th

I won't use it an extremely formal text.
But what does it mean?

Goodman, could it be considered as snitching?

blow the whistle Slang

To expose a wrongdoing in the hope of bringing it to a halt: an attorney who blew the whistle on governmental corruption.

http://www.thefreedictionary

Here is a link to the definition in the Cambridge Dictionary:
http://dictionary.cambridge.org/define.asp?key=8257&dict=CALD

I don't think all dictionaries will categorize this expression as "slang". I think calling it an "informal idiom" is much more appropriate.

Snitching is the slang version of whistle blowing.

For your questions....

I know Mr. X from work who is also my friend, but I also knew that he has been cheating the company and I wrote an anonimous letter to his boss. Which is the part that you don't under stand?

Someone asked flo ride about the lyrics and according to him, Ibelieve that the song isabout a sport called netball icachucha he was an umpire. About training the new umps and things like that. I think people will interpret a song however they want really- I don't deny that it has some... "insinuating" phrasing, bc I thought the song was about oral *** when I first heard it- but I do research on

In london before the telephone residents in the city would all have whistles. If they needed help one would blow their whistle outside their home and hopefully the policeman on the street would hear them and come.