Definition
Adjusting the day's load or volume to how the lifter actually performs, using a rule agreed in advance.
The programme sets the target and the client's body sets the weight. Readiness swings 5 to 10% from day to day, and a fixed percentage misses both the good days and the bad ones.
The common methods: RPE-based loading (3 x 5 at RPE 8, whatever weight that is today); a top set with back-offs (work up to a single at RPE 8, then 3 x 5 at 90% of it); and rep tests (an AMRAP set decides next week's load).
It needs guardrails or it becomes "whatever I feel like": cap the top set, forbid RPE 10, and keep a minimum volume so a bad day is still a session.