What? What did you say?

what / that thing (used in place of words you can't remember at the moment.)

Nothing

What?, Huh?

mince, minced meat

(adverbial particle, dismissive, derogatory) emphasizes disgust, contempt, or otherwise negative feelings of the speaker: whatever

何: interrogative pronoun; what

何か: something

Used other than figuratively or idiomatically: see なに, これ.

何者: someone; anyone / 何物: what