Asking the AI to do a task without showing it any examples. Just describing what you want.
Zero-shot means zero examples in the prompt. You rely entirely on the model's training to understand the task from your description alone. Modern LLMs are strong zero-shot learners - they can usually figure out 'classify this as spam/not-spam' or 'translate to Spanish' with no examples, because those tasks were well-represented in training.
Zero-shot works until it doesn't. For common tasks, it's the fastest path to a working prompt. For niche, ambiguous, or custom-format tasks, you'll need few-shot examples instead. Start zero-shot; escalate to few-shot when quality slips.