Source : Webster's Revised Unabridged Dictionary (1913)

Subduction \Sub*duc"tion\, n. [L. subductio.]
   1. The act of subducting or taking away. --Bp. Hall.

   2. Arithmetical subtraction. --Sir M. Hale.

Source : WordNet®

subduction
     n : a geological process in which one edge of a crustal plate is
         forced sideways and downward into the mantle below
         another plate