sub·duc·tion I. \-kshən\noun (-s) Etymology: Late Latin subduction-, subductio, from Latin subductus (past participle of subducere) + -ion-, -io -ion 1. a.: the act of taking away : withdrawal b.: arithmetical subtraction; also: deduction 2.: the act or process of subduing II. noun : the action or process of the edge of one crustal plate descending below the edge of another • subductverb