ˈbōlə̇n, -ˌlīn noun
Etymology: Middle English bouline, bowelyne, perhaps from bowe bow + line — more at bow , line III
1. : a rope fastened near the middle of the perpendicular edge of a square sail and used to keep the weather edge of the sail taut forward when the ship is close-hauled
2. or bowline knot : a loop knot that neither slips nor jams used especially for mooring and hoisting — see portuguese bowline , running bowline , spanish bowline