Source : Webster's Revised Unabridged Dictionary (1913)

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.

   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.

            He [Frederic the Great] drilled his people, as he
            drilled his grenadiers.               -- Macaulay.

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

   2. A training by repeated exercises.

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

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.

Source : WordNet®

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