top·sail /ˈtɑpˌsel, səl/
  上桅帆
  Top·sail n. Naut. In a square-rigged vessel, the sail next above the lowermost sail on a mast. This sail is the one most frequently reefed or furled in working the ship. In a fore-and-aft rigged vessel, the sail set upon and above the gaff. See Cutter, Schooner, Sail, and Ship.
  Topsail schooner. Naut. See Schooner, and Illustration in Appendix.
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  topsail
       n : a sail (or either of a pair of sails) immediately above the
           lowermost sail of a mast and supported by a topmast