气流 (qì liú) is a technical noun meaning 'airflow' or 'stream of air' — the movement of air in a specific direction, often in meteorology, aviation, or ventilation. It differs from 空气 (kōng qì), which is 'air' as a substance or atmosphere, and from 气息 (qì xī), which is 'breath' (the air you breathe out) or a figurative 'aura'. Think of 气流 as air in motion, not just air.