From Diablo Wiki

Jump to: navigation, search

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.

Arcane Damage: Critical hits from arcane damage silence targets for 4 secs. (Silenced targets can not cast some spells, such as a Skeletal Summoner or Goatman Shaman resurrecting fallen minions.)

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.