A disease where a musical instrument (most likely made of brass) becomes cold. The cold makes it harder to play the instrument, especially when it uses a mouthpiece.
Cases of cold horn usually occur in cold climates (duh) or transporting the instrument outside while it is cold. (once again, duh)
This can be avoided by keeping the instruments mouthpiece in a warm place, like a pocket.
Another way to avoid it (if your a trombone, trumpet, etc player) is to buy a plastic mouthpiece
Connor: Ahhhh dude, I got cold horn while walking in here.
Quinten:Haha, sucks dude, I had my mouthpiece in my pocket, so mine is warm.
Good luck with that high F.