1. (noun) a loop in a rope

• loop

2. (noun) a bend or curve (especially in a coastline)

• bend
• crook
• turn
• twist

3. (noun) a broad bay formed by an indentation in the shoreline

• bay
• embayment

4. (noun) the middle part of a slack rope (as distinguished from its ends)

• center
• centre
• midpoint

5. (verb) fasten with a bight

• fasten
• fix
• secure