T= Hitbox with Transcendent priority
P = Move with projectile priority
A = Air move
G = Ground move
T: anything = no clash
P: A/G = clash, P:T = no clash
A
= clash, A:anything else = no clash
G
= clash
G:G = clash unless % difference between moves is 9 or greater, in which case the stronger move continues while cancelling out the other.
And B-moves act as A/G depending on where they're used.
MK's nado is both a B-move with projectile priority. Thus, if MK nados while on the ground, if one of its hits clashes with something (it'll clash with anything that isn't transcendent), nado stops.
In the air, however, that one hit will be cancelled out but the nado continues, so another hit will just hit the opponent, which is why nado is so good. And it's why if you try to hit it with a non-transcendent aerial, you have to aim it to go between the hitboxes.
Not all aerials act as air moves. eg ZSS' nair has projectile priority
Not all projectiles have projectile priority. eg Falco's lasers are transcendent.
Ground moves can have transcendent/projectile priority, but most don't.
Edit: **** you Mekos XD