Pre-vent′er.
(Nautical.) An additional rope, spar, chain, or bolt, as a support, stay, or substitute. A supplementary or auxiliary rope to support a spar, stay, etc., in a gale or in action. A prcrenter-bolt is driven at the lower end of the preventer-plates to assist the strain of the chainbolts. Preventer-plates are placed below the links of the chains.