Glossary of Terms for Call of Cthulhu CCG

active player: The player who is currently taking their turn.
defending player: The player who is currently not taking their turn.
card effect: Any effect in the game that was triggered through the cards. This includes triggered effects and the triggering of story effects.
game effect: Any effect that does not stem from the use of the cards in play. This includes the effects which result from resolving a story, such as a character going insane due to the terror struggle, or the wounding of a character from the combat struggle.

Timing

action¹: Taking an action is when a player plays a card from their hand, or triggers character or support card abilities. Each action must be played and fully resolved before the next action can be taken by either player. Taking an action will pass priority to the next player.
priority: A system by which you determine whose turn it is to take actions. During the game, priority passes back and forth between the active and defending players. Priority gets reset to the active player at the start of each action block.
action block: The section during each phase of the turn where both players are allowed to take actions. In the timing chart in the advanced rules section, action blocks are shown as white boxes. Please note that the entire Operations phase is one large action block.
triggered effects: Every event card or character/support ability which is preceded by one of the four types of actions (Action, Response, Forced Response, Disrupt). They generally have requirements that you must meet, targetting choices, and a cost associated in order to trigger the particular effect.
triggered abilities: Triggered effects which are found on character or support cards.
Action¹: Triggered effects which are preceded by "Action:" in bold on the card. These can only be triggered during action blocks, and this passes priority to the next player after its effect (and any subsequent Responses, Forced Responses, and Disrupts) has been fully resolved.
Response: Triggered effects which are preceded by "Response:" in bold on the card. These can only be triggered after their response trigger has been met. You must play Responses within the response window, before priority gets passed and either player moves on to playing additional actions.
Forced Response: Triggered effects which are preceded by "Forced Response:" in bold on the card. These must be triggered after their response trigger has been met. They are similar to Responses, but are not a subset of them, and must be treated as unique. Please note that Forced Responses trigger immediately, regardless of what phase you are in.²
Disrupt: Triggered effects which are preceded by "Disrupt:" in bold on the card. These are the only types of actions that may be played out of sequence (ie: before the previous action fully resolves), and they must be played before the action resolves and the response window opens. Please note that Disrupts may be used at any point, regardless of phase, as long as their response trigger has been met.²
responsive actions: Triggered effects which require a trigger before they can be played. This includes Responses, Forced Responses, or Disrupts.
response trigger: This is the criteria (written on the card) which determines when you may play responsive actions.
response window: This is the timespan immediately following the resolution of an action, during which Responses (and Forced Responses) which have met their criteria may (or must) be triggered. This window closes when the next action which is not a Response (or Forced Response) is taken.
passive effects: Passive effects are ongoing effects that are not optional, unless otherwise stated. Passive effects and abilities do not require a response trigger for their effect.
Example: Decrepit Mausoleum (FR R137) - "Lower the cost for each player to play cards by 1 (to a minimum of 1)."
responsive passive effects: These are passive effects which are constantly checking for their response trigger in order to execute their effect. They fire immediately once the trigger has been met, and do not affect priority.
Example: Feasts of Locusts (EE C117) - "Sacrifice attached character at any time its controller controls 5 or more characters."

¹ It is extrememly important to recognize that the term "action" is different from the term "Action", and all definitions using these words should be read with the capitalization in mind.

² As explained in the timing flow chart in the rules, no actions may be taken during the resolution of the stories. After all stories have been resolved, you may then play Responses to anything that happened during the course of those story resolutions. Please note, however, that Forced Responses and Disrupts ignore this rule and must trigger immediately.

Priority/action Timing Diagram

The following is an intricate timing diagram of how actions are played out and the passing of priority from one player to the next. Please remember that this diagram is recursive, so everything in Step 2 must be played out for each action taken by either player. Also, priority toggles back and forth with the playing or passing of each action. Like hitting a chess clock, it is independent of the action tree and does not get reset when you start or come out of a "nested" action section.

Priority is clearly the most complicated part of the entire process, but its actually fairly simple if you don't think about it. Or, if you over think about it and analyze it to the obsessive point that I have. :-) If you would prefer not to get too wrapped up in largely unnecessary timing rules, just remember that each time you take an action (or pass the chance to do so), priority then passes to your opponent. If you keep in mind that both people passing the chance to take a response merely bring priority right back to the appropriate person, it all becomes relatively simple.

The one important exception to this is Disrupts, which work under their own priority system, separate from the main "chess clock". This separate system completely ignores current priority, always defaults to the active player, and resets itself each action. The benefit to all of this is that cancelling another player's action does not mean you've passed your turn to take the next action.

Active player has priority. They may:

Pass their action, thus passing priority. (Start diagram over with the next player.)
Take an action, thus passing priority.

A window opens for either player to play Disrupts, with an indepedent, internal priority system. priority_D starts with the active player, and passes back and forth until all Disrupts have been played and both players have passed additional actions. (If any Disrupts are played, each one is its own action, so you must begin the flowchart again at step 2, and return here once finished.)
If the action has not been cancelled by a Disrupt, resolve the action fully.
A response window now opens where any player may play responsive actions.

Any Forced Responses must trigger immediately. (If any do trigger, each one is its own action, so you must begin the flowchart again at step 2, and return here once finished.) If more than one would trigger, follow procedure for simultaneous effects found in the FAQ.
Both players now have the chance to play Responses, beginning with the player who has priority and passing back and forth until all Responses have been played. (If any Responses are played, each one is its own action, so you must begin the flowchart again at step 2, and return here once finished.)

The action and all responsive actions have been played. (Start diagram over with the next player.)

Proof of Concept

Below is a fairly simple explanation of my timing diagram and the idea governing it. While reading, please keep in mind that after every step priority has passed to the other player.

Active player plays Shotgun Blast, targeting opponent's Field Researcher.

Active player passes Disrupt.
Defending player passes Disrupt.

* Shotgun Blast resolves. No Forced Responses trigger.

Defending player triggers Field Researcher's Response text.

Active player passes Disrupt.
Defending player passes Disrupt.

* Defending player's character and support cards ready. No Forced Responses trigger.

Active player passes Response.
Defending player passes Response.

* We now return to Responses to the FR hitting the discard, getting wounded, getting destoryed, etc.

Active player passes Response.
Defending player passes Response.

* Move on to next action (priority is with Active player).

Even in this simple scenario, you can see the considerable number of times priority passes back and forth between each player. If this is making your head hurt (like it did for me), just remember that it plays out much in the same way that you expected it would before I ever bothered you with the intricate details of the process. Active player plays a shotgun blast, defending player uses Field Researcher response, now we go back to Active player.

Moral of the story is, don't think too much about it and just enjoy this wonderful game. :-)