A small click sound used by people expressing disappointment or discern during public speaking. It is not commonly used by people unless disappointment is implied to be exaggerated.
Monday morning in first period class..
Teacher: Attention students, your test has been moved to this Wednesday instead of Friday because a substitute will be filling in for me Thusday and Friday.
While the entire class is filled with sighs and "awww man!"s, Christine talks to Ryan..
Christine (addressing Ryan): Can you believe that? It's soo not fair!
Ryan (pushes tongue towards the back of the front teeth with lips closed and sucks in a small amount of air while opening the lips to make a brevorhetoric interjection addressed towards Christine): Yeah! *insert brevorhetoric interjection* Tell me about it.