1. [n]  the act of drilling a hole in the earth in the hope of producing petroleum
2. [n]  the act of drilling

DRILLING is a 8 letter word that starts with D.

1. \Drill"ing\, n.
   1. The act of piercing with a drill.
   
   2. A training by repeated exercises.
   
   

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

3. \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.