Async Race - A race where participants are not required to run at the same time. This allows players the convenience to race as their schedule allows but requires those involved to avoid spoilers until they have completed their run.
Dead Check - A check which does not directly provide progression. Examples include checks which reward an item or a character/esper/dragon after the requirement has already been met.
Fixed Encounter or Event Encounter - An encounter which occurs at a specific tile/location or by interacting with an entity and cannot be avoided by wearing Moogle Charms. Some examples include: Opera House Rats, Burning House flames, Imperial Camp soldiers, Lete River and Serpent Trench encounters, IAF battles, and during the Floating Continent escape and Magitek Facility Mine Cart Ride.
KAN or K@N - Kefka At Narshe check.
KT - Kefka's Tower. The final dungeon which must be completed to finish the game.
Moogle Charm - A relic which prevents random encounters when worn by any character in the active party. Flags optionally allow for starting with Moogle Charms and letting every character equip them.
RNG - Random Number Generation. Refers to something that is/was decided at random.
Seed - May refer to either the user definable flag or a particular instance of the game depending on context.
SOTW - Seed of the Week. Each week a set of flags and a seed is selected and made available in Discord. Everyone is welcome to participate.
Vanilla - Refers to something unmodified from the original Final Fantasy VI.
WOB and WOR - World of Balance and World of Ruin. The two worlds of Final Fantasy VI which may be accessed from the airship in Worlds Collide.