When Donald Trump learns new information that most people have known for a long time, and then he explains it to us in the way that it was just explained to him as if he's teaching us something that we didn't already know. Often preceded by the phrase "many people don't know..."
When Donald Trump says what he really feels. His supporters see it could be a damning statement then twist the story explain what he meant to say even though it isn't.
"Why wouldn't Trump denounce white supremacy during the first 2020 presidential debate?"
"Trump has always denounced white supremacy, he didn't need to. When he said stand back and stand by, he meant to let them by."
"You don't have to Trumpsplain to me why you support a racist."