Expressing disapproval is a common way to show one's dissatisfaction with something. Booing, tsk-ing, and hissing are all examples of expressed disapproval. Booing is a loud, vocal expression of disapproval, usually done in a group setting. Tsk-ing is a sound made with the tongue to express disapproval or disappointment. Hissing is a sound made with the mouth to express disapproval or contempt. All three of these expressions are commonly used to show disapproval in a variety of situations.