It is a Hebrew Word for the Foreskin that gets chopped off at birth. So when a person that is educated or a Jew calls you a Smuck. He or She is calling you a useless piece of dick.
I.E. a Smuck would go see the 2008 movie "never back down" or do things in attempt to appear "bigger" or manly. But factually a Smuck is weak and lame poser. Not so different from a Bro or a Gangster/Wangster.