The result occuring a day or so after smoking spice (such as K2) in which you experience slight memory loss and feel rather stupid for the whole day. Experts believe this is just a mental paranoia experience that can lead you to think you have something wrong with your brain.
Johnny- Fuck, I forgot about that homework, dude!
Tom- Probably cause of that K2 you smoked the other day.
Johnny- I think my brain is messed up dude!
Tom- You have massive Mush-Brain!
Johnny- Fuck Mush-Brain.