Chuptz is a sound/exclamation not really a word which the "macking of the lips" make when one is upset or dissaproves of something. Also the sound can be made in place of "Yeah right!" I have noticed that it's usually sounded off with very little lip space and without moving the jaw and no space between the upper and lower teeth. (I believe this originated in Africa but I hear it exclaimed by Latino people and especially those in the Caribbean a lot.)
"Chuptz! You didn't write that poem, you too stupid!"
Train station announcement: "The train will be delayed to this station" Those waiting for the train: "Chuptz!"