Luff

Luff has two meanings on a boat:

• As a noun, luff refers to the forward edge of a sail, or the area of the sail near the forward edge.

• As a verb, a sail is said to luff when it flaps or shakes in the wind due to its angle to the wind being too small. Luffing of the sail can be ceased by trimming the sheet, or by bearing off -- both procedures serve to increase the angle of the sail to the wind.