Torchlight 2 has many status effects that can be applied to monsters. However, they seem to be poorly documented (if at all.) One of these is
silence, which has a spell dedicated to it, is a byproduct of the nether imp's attack, and is an effect produced by many magical weapons.
Its official spell description is this:
Silences enemies within 8 meters, preventing them from using most skills.
Which abilities/monsters are affected? (The only one that I think I've noticed is the basilisk's immobilizing gaze.)