Source : Webster's Revised Unabridged Dictionary (1913)

Excavator \Ex"ca*va`tor\, n.
   One who, or that which, excavates or hollows out; a machine,
   as a dredging machine, or a tool, for excavating.

Source : WordNet®

excavator
     n 1: a workman who excavates for foundations of buildings or for
          quarrying
     2: a machine for excavating [syn: {power shovel}, {digger}, {shovel}]