NAK

NAK /nak/ interj.  [from the ASCII mnemonic for 0010101]
   1. On-line joke answer to {ACK}?: "I'm not here."  2. On-line
   answer to a request for chat: "I'm not available."  3. Used to
   politely interrupt someone to tell them you don't understand their
   point or that they have suddenly stopped making sense.  See
   {ACK}, sense 3.  "And then, after we recode the project in
   COBOL...." "Nak, Nak, Nak!  I thought I heard you say
   COBOL!"