Can Ornn's searing charge destroy Yasuo's windwall?

It's not terrain ..

Nope. The only collision that Wind Wall has is with projectiles that supposed to be blocked.

Here: https://leagueoflegends.fandom.com/wiki/Projectile

In that link, you can learn all about what can, and can't, be blocked by Yasuo's wind wall (W) or Braum's Unbreakable (E).

For champion-created terrain, these are the only one considered as walls/terrain:

• Crystallize (Anivia's W), Emperor's Divide (Azir's R), Jarvan IV's Cataclysm (R), and Pillar of Ice (Trundle's E).

---> Source: Vayne's ability details on her Condemn (E) and its interaction with player-created terrain: https://leagueoflegends.fandom.com/wiki/Vayne

Yasuo's Windwall blocks Aatrox Q btw. Found this out the other day.

it's not terrain because it does not function like terrain

in fact, it's the literal opposite of terrain in every way https://i.imgur.com/GUNxGSS.png[]