Preventer

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