The Collaborative International Dictionary of English v.0.48:

Drill \Drill\, v. t. [imp. & p. p. Drilled; p. pr. & vb. n.
   Drilling.] [D. drillen to bore, drill (soldiers); probably
   akin to AS. pyrlian, pyrelian, to pierce. See Thrill.]
   1. To pierce or bore with a drill, or a with a drill; to
      perforate; as, to drill a hole into a rock; to drill a
      piece of metal.
      [1913 Webster]

   2. To train in the military art; to exercise diligently, as
      soldiers, in military evolutions and exercises; hence, to
      instruct thoroughly in the rudiments of any art or branch
      of knowledge; to discipline.
      [1913 Webster]

            He [Frederic the Great] drilled his people, as he
            drilled his grenadiers.               -- Macaulay.
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The Collaborative International Dictionary of English v.0.48:

Drilling \Drill"ing\, n. [G. drillich, fr. L. trilix having
   three threads, fr. the of tres three + licium a thread of the
   warm. See Three, and cf. Twill.] (Manuf.)
   A heavy, twilled fabric of linen or cotton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Drilling \Drill"ing\, n.
   1. The act of piercing with a drill.
      [1913 Webster]

   2. A training by repeated exercises.
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The Collaborative International Dictionary of English v.0.48:

Drilling \Drill"ing\, n.
   The act of using a drill in sowing seeds.
   [1913 Webster]

WordNet (r) 3.0 (2006):

drilling
    n 1: the act of drilling [syn: drilling, boring]
    2: the act of drilling a hole in the earth in the hope of
       producing petroleum [syn: boring, drilling, oil
       production]