As I said before, test if the hitbox is truly independant from the character to see if it's a projectile.
If mario/pit reflects it, does the character move?
Does it cause hitstun when it hits?
If not, then it's not a projectile. Both of those test the same thing.
That's too complicated. It takes too long to test that, although testing if the hitbox is truly independent from the character would be a good way to go about it... if not for the fact that franklin badges are just easier to use and you can't really test if fox's/falco's dthrows are independent from them unless you use a franklin badge/reflector as they throw...
Also, Fox's lasers produce neither hitstun nor hitlag. They would not fit the second portion of your definition. However, it is common knowledge that they are, in fact, a projectile.
I think Sakurai specifically made Fox's lasers to work that way just to screw up our definitions of projectiles lol.
Otherwise, we have endless debates about the meaning of words, and unfortunately, categorizations are useful enough that we can't just drop them.
I must admit, it was quite fun though. It's not like anything truly metagame-changing ever goes on in this thread, anyways.
So no, redefining the english language and correcting it when they don't use YOUR version of it is not an option, it just confuses people and causes endless debates.
Adjectives are your friend.
But that's language evolving, that's slang ultimately becoming part of the vernacular.
It happens naturally, trying to force it simply confuses and annoys people.
We can still try! It's totally tubular to rewrite the English language.
But really, we're only doing this to cut down on the amount of over-technical people who come in and nitpick at what is/isn't a projectile, really. No real competitive use other than to cut down on the nitpickers. Sorta like differentiating between a glitch and an exploit. A glitch is when you do something by exploiting the game mechanics to produce something funky. An exploit is when you do something by exploiting the game mechanics to produce something funky, but is justified because it coincides with basic game physics, which a glitch can be.
And we have a winner!
Yeah, now I can fix my definitions.
Can't we just go with the old definitions? Projectile, attack, disjoint, and funky/weird/special attacks/hitbox? It's not like it really matters what they're called. It doesn't really mean much if we change the wording, so let's just go with what we're used to. The entire argument was just for the sake of nitpicking, after all. =D
Also yeah, Ness's Fair is a looped normal hitbox with sparkles. Special collisions are generally used in special moves, such as the Mach Tornady, but are occasionally spread around for super secret awesome moves, like the Knee (just to nerf it so it can't reverse. :X) or ZSS dsmash.
Also, to clarify, if someone replaces the special hitbox on the knee with a normal one, the knee will be able to reverse again. =D