What does NSURLConnection's error code "-1009" mean?

When I send a request and get an error with the error code -1009, what does that mean? I'm not sure how to handle it.

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
      NSLog(@"connection didFailWithError");

   if(error.code==-1009){       
      //do something           
   }    
}