[1] : The Collaborative International Dictionary of English v.0.48

sapper \sap"per\, n. cf. f. sapeur.
   one who saps; specifically mil., one who is employed in
   working at saps, building and repairing fortifications, and
   the like.
   1913 webster

[2] : WordNet (r) 2.0

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

Sapper >> S Words
Sapper, definition of term: Sapper
sapper_pag1.html