Compared to my Savage 25-06 rifle, my 8-3/8" M27 looks like a snubby!

Just kidding!
The snubby/stubby question (what is a it) has never formally been established that I could ever find. So, I think I have to go with the "traditional" view point; 2" or shorter.
I don't think you can add caliber, as the subject is mainly the size of the barrel, and secondarily the bulk of the gun. A snubby is supposed to small and easily worn or dumped in a pocket. Any 2" 5 or 6 shot revolver of J or K frame proportions would most likely qualify. L frame size is borderline.
Sorry, but N frame size is just too bulky to qualify. Not that they aren't practical, or useful, or whatever you might call them. They are short barreled "big" guns. Would you call a sawed off shotgun a snubby. I've seen them sawed off to about 6" of barrel past the end of the shell, with the stock shorted to the end of the pistol grip. Definitely a "short" shotgun, some might even call it a snubby shotgun. But it's just a short one (illegal as well, but not when I held it, a long time ago)

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Of course, this is just my opinion, and a few others that I know, but it doesn't make it "law". It certainly is entertaining to jawbone about it though.
Just my $0.02 worth of gasoline to add to this fire!