You searched for: “understatements
understatement (s) (noun), understatements (pl)
1. The assertion that something is not completely up to the standard or extent to which it is true: To say that the cake tasted good was a total understatement because it was beyond being delicious!
2. The usage of mentioning that things are of much less quality or caliber than they really possess: Jack told his friends in a gigantic understatement that he had a slight cold, when in reality he was in the hospital with a severe illness.