back·stay /-ˌste/
  後部撐物
  Back·stay n.
  1. Naut. A rope or stay extending from the masthead to the side of a ship, slanting a little aft, to assist the shrouds in supporting the mast. [Often used in the plural.]
  2. A rope or strap used to prevent excessive forward motion.
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  backstay
       n : a stay that supports the back of something