English phonetic spelling of Sicilian-American way to say "understand" (in the second person singular). Common in Mob movies. Typically used at the end of the sentence in these movies to verify the listener understands, especially when making threats. Comes from Italian obviously; it's basically capisci or capisce (depending on the context) with the last letter omitted from the pronunciation.
You better make sure your boss is outside the saloon at high noon, capish?