A sentence using the meaning of understatement?
Someone said it would be difficult to climb Mount Everest. I said that was an understatement.
To say that the Nazis killed several thousand Jews is a huge understatement. His admission that he had some troubles as a teen was a vast understatement, as he was twice questioned concerning gang killings. An understatement is explaining something in simple or trivial terms when, in fact, the idea being explained is complex. To say it's cold outside today, is an understatement.