Anyway it's the most used in Italy, and it's one of the main words that a foreigner learns when he comes in Italy, together with "ciao", "arrivederci", "caffè"...
- a pain after an hurt ("porcoddio che male! - porco dio what a pain!");
- an exclamation of surprise ("porcoddio che spettacolo! - porco dio what a show!");
- an exclamation when you are doing a job that doesn't works ("eee porcoddio guarda se sto cazzo de chiodo entra ner muro! - eee porco dio look if this shit of nail goes in the wall!").