Luffing is a sailing term that refers to the act of turning the boat's sail away from the wind, or allowing it to flap as the boat changes direction. Some synonyms for luffing include fluttering, flapping, billowing, and sagging. These words describe the movement of the sail as it loses its power and effectiveness, which can cause the boat to slow down or lose control. Other words that can be used to describe luffing include drifting, veering, oscillating, and swaying. Understanding the various synonyms for luffing can help sailors communicate more effectively and maneuver their boats more safely and efficiently on the water.