Tut-tut is defined as something said to show annoyance or to call someone on bad behavior.(interjection)
An example of tut-tut is what someone says when talking about a congressman who got caught in a sex scandal.
See tut-tut in Webster's New World College Dictionary
interjection, noun, intransitive verb
See tut-tut in American Heritage Dictionary 4
intransitive verb tut-tut·ted, tut-tut·ting, tut-tuts