Judgemental resolution is a type of resolution in which outcomess are determined solely through the choices of the players (most commonly the GM) rather than by game mechanics. Judgemental resolution is referred to as drama in the terminology of GNS Theory and the Big Model. When a GM applies GM fiat to resolve a conflict, that is a type of judgemental resolution, and judgemental resolution may sometimes be referred to as fiat.
No games use judgemental resolution for all situations, as this would go against the assumption that role-playing games are at least partly adjudicated according to rules. However, judgemental resolution is very common, with many actions in role-playing games being decided by judgemental resolution even when this isn't stated explicitly. In fact, judgemental resolution is implicitly assumed to be the default method if no other game mechanics are specified in a game's system. For example, if a character wants to pick up a scrap of paper that they find in a new location in the game world, it's generally assumed that they do so without consulting dice (random resolution) or checking relevant statistics (deterministic resolution).
Many games use judgemental resolution for part of a game's resolution mechanic. In the IIEE model, intent and initiation are commonly resolved judgementally, with execution and sometimes effect resolved randomly (as in Dungeons & Dragons and other traditional role-playing games).
Some theories recommend judgemental resolution in certain situations even if a game's rules as written would require a mechanic. In particular, the common piece of GM advice that success and failure should both be interesting relies on the group or GM using judgemental resolution to decide outcomes when only one possible outcome would be satisfying. The rule of cool can sometimes be used to apply judgemental resolution in some cases. Fudging die rolls is also a form of judgemental resolution.