Used to politely tell someone that they just completely contradicted themselves. It can also be "Read that again, but slowly" if it's in text rather than actually being uttered.
Dumbass: "The Flat Earth Society has members all around the globe!"
Normal Person: "Say that again, but slowly..."
Normal Person: "Say that again, but slowly..."
by Ubeenbamboozledson September 23, 2021