COLLAR A FOLLOWER of fashion and ask him to define spezzato, and chances are he'll furrow a well-groomed brow. Outside Italy, even industry veterans don't seem to know the word. But if spezzato isn't on the lips of menswear aficionados, it's everywhere they look—including, in all likelihood, the mirror.

Not to be confused with sprezzatura, which is the art of unstudied elegance, spezzato literally translates as "broken in two." Quite simply, it describes a combination of jacket...