The Polish word for white. It's also a type of roll, which Tony Soprano seems to be craving all time for no apparent reason.
Tony: "Yo Paulie, go get me a bialy."
Paulie: "Didn't you just eat one, boss?"
Tony: "Do you want me to cut your friggin' head off? I SAID, go get me a bialy!"
Paulie: "Sure thing, boss. Sure thing."