Shutdown is a term that describes using a certain amount of skills to render
a caster’s skill setup useless to make for an easy kill. For example, the
Mesmer skills Backfire and Migraine can be a caster’s worst nightmare and
can shut them down because of the fact that it will take longer to cast
skills, and even if they do get a cast out, they will take heavy damage for
them.

Shutdown characters are usually Me/R or a R/Me. However, shutdown characters
don’t just have to use Hexes; they can use Interrupts to shut a caster down
because of the fact that Hexes can be easily removed and shattered.

EXAMPLE: Monks are so useless when you shut them down with Backfire.