What is the name of the Xbox One controller's trigger-vibration feature?

The Xbox One controller's trigger-vibration feature is called Impulse Triggers.

Impulse Triggers are vibration motors built directly into the controller's left and right triggers. Unlike traditional rumble motors in the controller body, they can provide separate feedback through each trigger.

Games can use the feature to communicate events such as weapon recoil, braking force, collisions, or changes in vehicle traction. Forza Motorsport 5 was among the launch-era games that demonstrated how the triggers could convey driving feedback.

Impulse Triggers are part of the Xbox One controller design and were retained in later Xbox controllers. They are different from the adaptive triggers used by Sony's PlayStation 5 DualSense controller, which can change resistance as well as provide vibration.