a line used to secure the boom from swinging unexpectedly across a sailboat

An extra rope, to assist another. Prizing

Term applied to duplicated rigging. In some cases it seems to be used with its original - and literal - meaning of 'coming before'.

A rope used for additional support or for additional securing, e.g., preventer stay.

A line or other device that prevents an accidental jibe; as in: When running in waves and wind we usually rig a preventer.

A rope used for additional support or for additional securing, e.g., preventer stay.

A sail control line originating at some point on the boom leading to a fixed point on the boat's deck or rail (usually a cleat or pad eye) used to prevent or moderate the effects of an accidental [..]

A rope backing-up another line or rope that is under extra strain, to 'prevent' the latter from breaking or giving way.

(1) Line and blocks or the boom vang used to keep the boom in place while reaching or running and to prevent an out of control swing during an accidental jibe. (2) Any additional line or wire temporar [..]

 A sail control line that prevents accidental jibes.

line and/or tackle which limits the movement of the boom, usually for the purpose of preventing accidents or-An extra rope, to assist another-

(1) Line and blocks or the boom vang used to keep the boom in place while reaching or running and to prevent an out of control swing during an accidental jibe. (2) Any additional line or wire temporar [..]

One who, or that which, prevents. (nautical) An arrangement, made with ropes and blocks, that prevents the boom of a sailing boat from performing a jibe. (nautical) Any of various lines set up t [..]