When at low health, occasionally rogues can narrowly escape brushes with death.
If you are in light or no armor and at below 20% of your hitpoint maximum, each time you are struck with an attack there is a percentage chance equal to your Reflex save that the attack does half main damage, and its special effects are negated (as if you were blocking).
For example, if a rogue has 250 hitpoints and reflex 29, then whenever she is at 50 or fewer hp, there is a 29% chance attacks will do 50% damage.
Notes
Tabaxi can gain this feat from racial enhancements