The Collaborative International Dictionary of English v.0.48:

Tamping \Tamp"ing\, n.
   1. The act of one who tamps; specifically, the act of filling
      up a hole in a rock, or the branch of a mine, for the
      purpose of blasting the rock or exploding the mine.
      [1913 Webster]

   2. The material used in tamping. See Tamp, v. t., 1.
      [1913 Webster]

   Tamping iron, an iron rod for beating down the earthy
      substance in tamping for blasting.
      [1913 Webster]