From Diablo Wiki
Silence is a term meaning to stop a player or monster's ability to cast spells such as resurrection and buffs. It was first seen pre-game, as a critical hit property of the Arcane type of damage.
This property does not seem to exist in the final game; all of the special bonus effects for various types of critical hits were removed during development, and if Silence was preserved anywhere, it's called by a different name.
- See more Reference terms.