Soak is used to determine how resilient and durable a character or an object are to damage in a roleplaying game.
The Storyteller System uses the Stamina Attribute (and in the case of some supernatural powers like Fortitude) as a dice pool to roll to subtract from damage once inflicted. 
In the variant on the Storyteller System used in the Trinity Universe games, bashing damage is soaked using Stamina. In the games Adventure! and Trinity, there is an option that allows characters to soak lethal damage. In Aberrant, being able to soak lethal damage is automatic for novas . In all cases, the soak is automatic and is not rolled like it is in the standard Storyteller System.
In First Edition Exalted, bashing and lethal soak are figured stats based on the Stamina Attribute. Soak is figured the same way as it is in the Trinity Universe. Soak is also automatic and not rolled like it is in the Storyteller System.
Second Edition Exalted games use the same method as First Edition Exalted and have different subcategories of armor, which may or may not stack with Soak (or each other) depending on type.
In the Storytelling System, Soak was replaced with Defense for Characters and Durability for objects. 
- ^ VTM: Vampire: The Masquerade Rulebook Revised, p. 224
- ^ CofD: World of Darkness: Storytelling System Rulebook, p. 36
- ^ Adventure!: Adventure! Rulebook, p. 200
- ^ Trinity: Trinity Rulebook (softcover), p. 240
- ^ Aberrant: Aberrant Rulebook, p. 241
- ^ Exalted: Exalted Rulebook, p. 231-232
- ^ Exalted: Exalted Second Edition, p. 149-150
- ^ VTM: Vampire: The Masquerade Rulebook Revised, p. 160,209
- ^ MTAs: Mage: The Ascension Rulebook, p. 238