Wordnet 3.0
NOUN (2)
1.
a military engineer who lays or detects and disarms mines;
2.
a military engineer who does sapping (digging trenches or undermining fortifications);
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]
WordNet (r) 3.0 (2006):
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)