Subduction

n. withdrawal, taking away, reduction; process of one plate of the Earth's crust being forced underneath another (Plate Tectonics)

In geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another, with one sliding underneath the other and moving down into the mantle, at rates typically measured in centimeters per year. An oceanic plate ordinarily slides underneath a continental plate; this often creates an orogenic zone with many volcanoes and earthquakes. In a sense, subduction zones are the opposite of divergent boundaries, areas where material rises up from the mantle and plates are moving apart.
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Noun
1. a geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate
(hypernym) geological process, geologic process

(n.)
The act of subducting or taking away.
  

(n.)
Arithmetical subtraction.
  

The sinking of an oceanic plate edge as a result of convergence with a plate of lesser density. Subduction often causes earthquakes and creates volcano chains.