sap·per /ˈsæpɚ/
  挖地道的兵,工兵
  Sap·per n.  One who saps; specifically Mil., one who is employed in working at saps, building and repairing fortifications, and the like.
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  sapper
       n 1: a military engineer who lays or detects and disarms mines
       2: a military engineer who does sapping (digging trenches or
          undermining fortifications)