1) A rope bent on to (for example) an anchor chain to hold it temporarily. Might also be a rope bent on to another (Rolling Hitch) to take the load off it while you make some adjustment.
Stopper (2) A device that instantly holds a sheet fast. Known also as jammers or as lock-offs in the USA, these valuable gadgets usually take the form of a lever operated cam which squeezes and grips the rope. They are commonly used with sheets and halyards, allowing several different ropes to be hauled taut by just one winch.