A Glossary of Tabletop Terms Rulebooks Use Without Defining

Roleplaying games have accumulated a vocabulary that circulates faster than it gets defined. Some of it is genuine jargon with a precise meaning; some of it is one designer's phrase that escaped into general use and drifted. Both kinds show up in reviews, forum arguments and rulebook introductions with the confidence of established terminology.

The definitions below are the working ones — what the term means when someone uses it at a table, rather than the strictest reading. Where a word means different things in different traditions, that is noted instead of smoothed over.

Terms

Action economy

How many meaningful things each side gets to do per round. One creature against four characters is losing four to one before any dice are rolled, which is why solo opponents need extra actions to hold a fight together.

The fiction

What is actually happening in the imagined world, as distinct from what the rules say. Games that talk about moves being "triggered by the fiction" mean the described action comes first and the mechanic follows it, never the reverse.

Session zero

A meeting before play to agree tone, content limits, scheduling, how characters know each other and which optional rules are in use. Skipping it does not remove the disagreements; it postpones them to session three.

Failing forward

Resolving a failed roll by advancing the situation rather than stopping it. The lock stays shut and the patrol arrives, instead of the lock staying shut and everyone rolling again.

Playbook

A character sheet that is also a character type, carrying its own abilities, questions and relationships. Common to games in the Apocalypse World tradition, where picking one does most of what character creation does elsewhere.

Target number

The value a roll must meet or beat. Called a difficulty class in d20 games, a target in dice pools, and simply the skill value in percentile systems, where you roll under it instead.

Dice pool

A mechanic where you gather several dice and count how many beat a threshold, rather than summing them. Adding dice raises reliability faster than it raises the ceiling, which is why pool systems feel steadier than d20 ones.

Advantage

Rolling twice and keeping the better result. Worth up to twenty-five percentage points on a coin-flip roll and under five on a desperate one, which is the opposite of how it is usually described.

Hit dice

An older measure of a creature’s toughness that doubles as a rough difficulty rating. Still the standard in old-school-adjacent games, where the referee is expected to judge the rest.

Sandbox

A campaign structured as a place rather than a plot. The referee prepares locations, factions and pressures; the players decide what the campaign is about by choosing where to go.

Railroad

A campaign where player choices do not change the outcome. Rarely a deliberate design and usually the result of preparing a story instead of a situation.

Downtime

Structured activity between adventures — crafting, research, recovery, building relationships. Systems that define it well give non-combat characters somewhere to be excellent.

Retainer

A hired non-player character who accompanies the party. Standard practice in early play, largely forgotten in modern games, and still the cheapest fix for a party that is one role short.

Safety tools

Agreed mechanisms for adjusting or stopping content during play, from a card on the table to a quick check-in. They work best introduced at session zero, as ordinary procedure rather than an emergency measure.

OSR

A loose family of games and design attitudes descended from the earliest editions: lethal, resource-focused, light on character abilities and heavy on player decisions. Less a ruleset than a set of assumptions about what play is for.

Bounded accuracy

A design approach that keeps numbers close together as characters advance, so a low-level threat never becomes mathematically irrelevant. The reason a large group of weak creatures can still matter at high level.

On terminology that travels badly

A recurring source of confusion is that several of these words describe a mechanic in one family of games and an attitude in another. "Failing forward" is a written procedure in some systems and a piece of refereeing advice in others; treating the advice as a rule produces a game where failure never costs anything, which is not what anyone intended.

The same happens with target numbers. Rolling high against a difficulty and rolling low against a skill value are mathematically interchangeable, but they read as opposites, and players moving between the two traditions routinely misjudge how hard a task is meant to be for the first few sessions.

Where a term appears in a rulebook without a definition, the safest assumption is that the author expected you to have played the game they learned on. Naming which game that was usually resolves the ambiguity faster than arguing about the word.

Common questions