One who goes before; one who forestalls or anticipates another. Bacon. [1913 Webster]
One who prevents or obstructs; a hinderer; that which hinders; as, a preventer of evils or of disease. [1913 Webster]
An auxiliary rope to strengthen a mast. [1913 Webster]
Preventer bolts, or Preventer plates (Naut.), fixtures connected with preventers to reënforce other rigging. -- Preventer stay. (Naut.) Same as Preventer, 3.