Definition
Human-in-the-loop means a person is part of the process: approving an agent's proposed payment, checking a drafted contract clause, or handling the cases the AI flags as uncertain. A related pattern, sometimes called human-on-the-loop, has people supervising and able to intervene rather than approving each step.
The EU AI Act requires effective human oversight for high-risk AI systems (Article 14). Done well, human review is targeted at the decisions that matter; done badly, it becomes a rubber stamp or a bottleneck that removes the benefit of automating.