1) Obviator 
A preventer, or jibe-guard, is a mechanical device on a sailing vessel which limits the boom`s ability to swing unexpectedly across the boat due to an unplanned accidental jibe. During an unplanned accidental jibe (or gybe), neither the crew nor the boat is set up properly to execute a planned jibe. As a result the uncontrolled boom will swing ac....
Chains attached to the hull and rudder to prevent a heavy sea from sweeping it away.
• (n.) An auxiliary rope to strengthen a mast. • (n.) One who prevents or obstructs; a hinderer; that which hinders; as, a preventer of evils or of disease. • (n.) One who goes before; one who forestalls or anticipates another.
A line set up to hold the boom in position and prevent an accidental jibe.
a control line from the boom to the toerail used to prevent unexpected gybes
Pre·vent'er noun 1. One who goes before; one who forestalls or anticipates another. [ Obsolete] Bacon. 2. One who prevents or obstructs; a hinderer; that which hinders; as, a preventer of evils or of disease. 3. (Nautical) An auxiliary rope to strengthen...
(Gybe preventer, Jibe preventer) 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 jibe.
a person or thing that prevents. · · any of various lines set up to reinforce or relieve ordinary running or standing rigging. · a line for preventing a sail from jibbing.