Pigs. It's not an insult as such, but that depends on what it's referring to.
In this case it's an acronym coined by "economic analysts" to describe the European countries that have been hardest hit by the recession: Portugal, Ireland, Greece and Spain.
Now, I happen to be Irish, but I'm not particularly nationally-minded, so on one level it doesn't bother me all that much. However, when you consider who these "economic analysts" are, and what their role has been in the crisis affecting Greece, it's a different story.