Definition of "preventer" [pre•vent•er]

• One who, or that which, prevents. (noun)
• An arrangement, made with ropes and blocks, that prevents the boom of a sailing boat from performing a jibe. (noun)
• Any of various lines set up to reinforce or relieve ordinary running or standing rigging. (noun)

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• "While it's still unclear why the blowout preventer did not work, Transocean chief executive Steven Newman said the preventer is not the ultimate cause of the accident."
• "And federal authorities have salvaged the well's blowout preventer from the bottom of the ocean to examine why it failed as a last-ditch tool to cap the leak."
• "Lest you think this review should earn less than a G-rating, tallywhacker is a legitimate nautical term for a "preventer" - a device that stabilizes the boom on the mainsail as you journey down-wind."