The Collaborative International Dictionary of English v.0.48:

Digger \Dig"ger\, n.
   One who, or that which, digs.
   [1913 Webster]

   Digger wasp (Zool.), any one of the fossorial Hymenoptera.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Diggers \Dig"gers\, n. pl.; sing. Digger. (Ethnol.)
   A degraded tribe of California Indians; -- so called from
   their practice of digging roots for food.
   [1913 Webster]

WordNet (r) 3.0 (2006):

digger
    n 1: a laborer who digs
    2: a machine for excavating [syn: power shovel, excavator,
       digger, shovel]