Tenacity
From ThresholdRPG Wiki
Tenacity is a mechanic which is used to ignore stuns during combat for a single round. Every mortal has an innate tenacity rating of 0. Tenacity rating may be improved through the use of abilities or magical items that confer buffs.
When necessary, as in the summary command, tenacity is displayed as a rating value rather than a percentage chance. This rating value (R) is used in the calculation of chance to ignore a stun.