"Brutto il signore" literally means "Ugly (the) God". The
Catholic Church is really powerful in Italy and insults to God, Jesus, Mary and all the other saints are very badly judged (it's actually a crime) but, at the same time, very common. People use "Brutto il signore" even to complain about anything, for example when they
accidentally hurt theirselves or it starts raining. It's particulary in the folk customs of the two regions of Veneto and Tuscany, where they use these kind of
expressions ("Dio Maiale", "Madonna Puttana", "Cane di Gesù" and so on) very often and at every age.
*a hammer or another heavy objects falls on one's foot*
(loud) "BRUTTO IL SIGNORE!!!"
"
I've been in queue for an hour to get
the ticket and so I missed
the last train, brutto il signore!"