The phrase "unspeakable crime" refers to a terrible act that is so shocking, horrible, or disturbing that it is difficult or impossible to describe or talk about. Full definition
All of these individuals were accused and / or convicted of committing unspeakable crimes against children. (empoweringparents.com)
A little more than two hundred years into the American experiment, cultural conservatives stand convicted of unspeakable crimes in the eyes of most of America's media commentators. (firstthings.com)
When English readers want to understand what it was about — how people lived and died inside a cult of personality that committed unspeakable crimes against its citizens — I hope they will turn to this carefully documented story. (amazon.com)