Has many crude/colloquial uses but literally means "This Dick".
fr Italian/Neapolitan Stu Cazzo
Stu is the way Questo (The Italian word for 'this') is pronounced in the Neapolitan dialect.
Cazzo means dick/prick ( lit. penis)
btw - It does not mean 'balls' as is frequently suggested.
You often hear the phrase in the movies "don't break my balls"
....which is a direct translation of the Italian:
"Non rompermi i coglioni" - (coglioni meaning balls/testicles)
Stugatz! (What a f**king idiot)
He lost everything In Vegas
How much does he have left?
Stugatz! (F**k all - nothing)
plus many others