“Oh, really?”

The crossword question “Oh, really?” is THATSO” is asking for a four-letter phrase that means “Is that so?” or “Really?” The answer to this clue is “THATSO,” which is a slang word made up of “that” and “so.” It is often used as a response to express surprise, disbelief, or skepticism when someone tells you something new or unexpected. This phrase has gained popularity in recent years and is commonly used in informal or casual conversation.