expression, interjection
What did you say?!; What's that?!
A confrontational or surprised retort, often used when the speaker is offended or incredulous about what was just said. Can be rhetorical or a genuine demand for clarification, depending on tone.
「お前、役立たずだな。」「何だと！」
"You're useless." "What did you say?!"
「明日から会社に来なくていいよ。」「何だと？」
"You don't need to come to work from tomorrow." "What's that?"