When a nasty hagatha looking bitch sneezes and because she's so full of shit her snot comes out looking like rust.
Dude, did you hear Sheryl? She just let out a Rusty Sneeze, stupid bitch.
A sneeze so powerful that it causes one to shit thy pants. Similar to a snart, yet messier. Can be used in both noun and a verb form.
Gee whiz! After last night a snart would have been understandable, but that rusty sneeze completely caught me off guard. Let me get a towel.