sheet anchor
  備用大錨,最後的希望,最後的手段
  Sheet an·chor
  1. Naut. A large anchor stowed on shores outside the waist of a vessel; -- called also waist anchor. See the Note under Anchor.
  2. Anything regarded as a sure support or dependence in danger; the best hope or refuge.
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  sheet anchor
       n : spare anchor for use in emergency [syn: waist anchor]