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 ?
If he asks me to jump, I won't do it, that's flat, and I don't care who the devil he is.
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.
e's blue in the face, but I ain't going, and that's flat.
Across:9, Out-fitter 10, Gets even 12, Gill 13, F-r-ight 14, Realise 15, That's flat 17, Trea-sure-d 18, Pick-L-ed 20, Parr-ot 21, Stun 24, Col-ossal 26, But-ted in 28, Eyed (I'd) 29, Cal-me-d 31, Shatt-er 34, Ag-reem-ent 36, Leaves out 38, Anatole 39, Re-ally 40, Rea-R 41, Goodness 42, Hands down.
Highly precise optics usually start with a rough-cut slab of glass that's painstakingly transformed to a polished, smooth surface that's flat to less than one wavelength of visible light.
Worry like a dog a bone, Wear out your every gramophone If it will help avoid a TONE that's FLAT.
Find a fingering that's flat and slowly scoop the pitch up.
Now Woolybacks aren't local No, they don't live round here They come from Crewe or Khatmandu Even Lake Windermere They don't speak proper English Not like you and me And watch those Mancs from up the Lancs They still eat missionaries you see He's dead unsophisticated Says thou instead of you Belt and braces on his trousers Wears a clog and not a shoe Stuffing ferrets down his trousers Wears a cap that's flat Speaks in a foreign language Like on Ilkey Moo Bahat (What does that mean?
You're not going [to deny it], because that's flat out insulting to the gay community.
Now, according to the internet he is gay and he can't deny it because that's flat out insulting to the gay community, he added.
Season to date, we're the only broadcast network that's flat from the previous season.
A pointy pair that's flat in the sole, and sexy-thin yet easy on the height is the way to go.
But if you give them something that's flat, there's no movement off the ball, it's slow and pedantic and you don't create anything of course it's going to result in a quiet atmosphere.
You can install the tile directly over any wall surface that's flat and sound, but clean the wall first so the adhesive will stick.
How to wear: This is one trouser that's flat shoe-friendly.