A mosher is a person who is crossed between goth/punk/skater they have long hair and listen to music like slipknot and metal music. Some people call them headbangers. At certain music shows they have something called a mosh pit, basically its a fight pit with loads of people bashing each other
If people at a rock concert mosh, they jump up and down together in front of the stage, often pushing each other. Moshing down the front, crushed against the stage in a sweat-drenched T-shirt is all part of the gig experience. to dance very violently at a concert with loud rock or punk music (Perhaps from mosh (19-20 centuries), from mush; MUSH)
To dance by intentionally jumping into and colliding with other, similarly behaving dancers, and performing other wild, aggressive, or spastic movements