Rollout
One sampled attempt at a task, start to finish, used to compute a reward during RL training.
A rollout is a single trajectory: the model is handed a task, acts until it finishes or gives up, and the whole attempt is scored by a verifier. RL algorithms like GRPO sample many rollouts per task and push the policy toward the ones that earned reward. Rollout throughput is often the real bottleneck in RL training.