that's flat

and that's flat!

old-fashioned And that (decision) is final! Look, I told you I'm moving to Canada after high school, and that's flat!
See also: and

that's flat

used to indicate that you have reached a decision and will not be persuaded to change your mind. informal
See also: flat
References in classic literature ?
I do not wish to gloss over any fault the prisoner may have committed, if such a fault exists; but we owe her some consideration, and that's flat!"
If he asks me to jump, I won't do it, that's flat, and I don't care who the devil he is." The bridge, as I say, was arched and covered in, in a very ridiculous manner, and there was a most uncomfortable echo about it at all times -- an echo which I never before so particularly observed as when I uttered the four last words of my remark.
'I don't know how much you've got, and I dare say you hardly know yourself, as it would take a pretty long time to count it,' said Sikes; 'but I must have some to-night; and that's flat.'
But if you think I am going to let the Union Jack go down and down eternally, like the bottomless well, down into the blackness of the bottomless pit, down in defeat and derision, amid the jeers of the very Jews who have sucked us dry--no I won't, and that's flat; not if the Chancellor were blackmailed by twenty millionaires with their gutter rags, not if the Prime Minister married twenty Yankee Jewesses, not if Woodville and Carstairs had shares in twenty swindling mines.
'e's blue in the face, but I ain't going, and that's flat. I'm
But I won't meet Rawdon Crawley, that's flat. I'll go over to Huddleston, that I will, and see his black greyhound, Mrs.
"I carn't," he said, "that's flat. I 'aven't the guts for it!
When the laptop is sitting upright at a 90-degree angle, you could type on the part of the screen that's flat, but screen typing isn't a very pleasurable experience.
Much will hinge, Litman said, on Cohen's knowledge of the circumstances surrounding the payments to McDougal and Daniels, and "whether Trump knew about them." Those payments, Litman said, "very possibly amount to wire fraud, and if Trump was in on them, that's flat out conspiracy."
"[Houston has] the worst of conditions - huge development and you're in terrain that's flat as a pancake.
The best cookware to use for this type of cooktops or ranges has to have a bottom that's flat, smooth, and magnetic.
LEARN SOMEWHERE THAT'S FLAT AND EASY MOST of us probably learned to ride a bike in a field of some sort, but grass can be hard work.
The main changes inside include a new three-spoke steering wheel that's flat bot- tomed for the AMG models with lashings of Nappa leather throughout.
Set it on a couple of sawhorses and you've got a surface that's flat and strong but lightweight and easy to store.
That's flat. "With such a long slim profile," wrote Sue French in 2013, "NGC 5907 has won the nicknames Splinter Galaxy and Knife-Edge Galaxy." For my money, NGC 5907 is the best flat galaxy in the northern heavens.