Just recently I was in a conversation with a number of UK mainlanders and we had a debate over what “tories” meant, apparently disproportionately ordinarily it refers to a political party and it’s not usual to use it as short for “territories” as I’ve used it (according to how the debate ended, it was half and half between them). And once again I’m reminded of how people feel to look back at their usage of a word/phrase over the years and cringe.
More tragically, me and a friend were embarrassed once upon realizing everyone was confusing “encephalitis” with “hydrocephalus” when talking to someone about their kid with hydrocephalus. Awkward because encephalitis is caused by HIV.
Understatement would be like “it’s just sprinkling” when it’s actually raining really bad. Typically used sarcastically when someone tries to compare the situation to something that is normally comparable but to a lesser degree.
Unless I am unclear on what you’re misunderstanding :)