there is some confusion if pigs should have one, two, or three "i"s. The term refers to either 

Portugal

Ireland

Greece,

Spain

or it may also include Italy, Iceland and Dubai (and exclude Spain) – depending on the various authors' assessments how bad the crisis is in the EU, and if it should include Iceland/Dubai as a non EU countries.

In this case, a picture is worth a thousand words. Floyd Norris from the New York Times outlines how the Greek fiscal crisis has led to contagion and a mild currency crisis in EU land.