It means "piece of shit" (in italian: "pezzo di merda", which is also used with the same meaning of "stronzo");
when used to denote a real piece of shit (not in the figurative way), it often denotes an oblong piece of shit.
- That bastard cheated me!
- Ho uno stronzo che sporge dal culo, dov'è il bagno?
- (lit.) I have a piece of shit that protrude from the ass, where's the wc?
- (not lit.) I need the wc very urgently!
- Il cane mollò uno stronzo di dimensioni bibliche.
- The dog dropped a piece of shit which had biblic dimension (i.e., so big that it deserves a special mention in an important book)
(Tra amici che giocano a carte, uno mette giù un poker) - Ma che stronzo!
(Among friends playing cards, one of them put down a poker) - What a bastard!
Commonly used as bastard, bitch, or son of a bitch
Leave me alone, turd!/asshole
Hai fatto una grande stronzata!
Lit: You made a big shit!
Fig: You really fucked things up!