Bight
A curved or folded section of rope between its two ends; in rope bondage usually the fold at the middle of a rope that is tied doubled.
In knot terminology a bight is any slack or curved part of a rope between its two ends, and a knot that can be made without using an end is said to be tied in the bight. Knot writers draw the edges differently: Clifford Ashley separates a bight from a narrower loop, while Geoffrey Budworth counts any U-shaped bend as a bight. In rope bondage, where rope is usually tied doubled, the word mostly refers to the fold at the middle of the rope (Rope365; Anatomie Studio). Shibari Study links it to the Japanese nawa gashira (縄頭), and Andrea Ropes explains that term as the head of the rope.