Torque
A shaft's resistance to twisting, measured in degrees - lower torque feels stiffer and more stable, higher torque feels smoother.
Torque measures how much a shaft twists along its length under rotational force, expressed in degrees. A shaft with 2 degrees of torque resists twisting more than one with 5 degrees. It is a separate property from flex - two shafts can share the same flex rating but feel very different because their torque differs.
Lower torque generally feels stiffer, more stable, and more controlled, and tends to suit stronger, faster swingers who would otherwise feel a shaft twisting on them. Higher torque feels smoother and softer and can help slower or smoother swingers feel the head load. Torque is felt as much as measured - it shapes the personality of a shaft.
Torque is mostly a consideration in graphite shafts, where it varies meaningfully. Steel shafts have inherently low torque and the spec is rarely discussed for them. In driver and fairway-wood shafts, where graphite dominates and speeds are highest, torque is a key fitting variable.
Like most shaft specs, torque is not standardized across brands and is best understood as one ingredient in overall shaft feel rather than a number to chase in isolation.