nah-uh
the ultimate no. it’s like saying 'you’re not even close' to being right. it’s when you hear something so wrong it makes you want to punch the person who said it.
"He said he could run a mile in 2 minutes. I said 'nah uh.' He ran it in 3."
"She said her grandma could swim the ocean. I said 'nah uh.' Her grandma took a boat."
"He said he could eat 20 tacos. I said 'nah uh.' He threw up."