Source : Webster's Revised Unabridged Dictionary (1913)

Decoction \De*coc"tion\, n. [F. d['e]coction, L. decoctio.]
   1. The act or process of boiling anything in a watery fluid
      to extract its virtues.

            In decoction . . . it either purgeth at the top or
            settleth at the bottom.               --Bacon.

   2. An extract got from a body by boiling it in water.

            If the plant be boiled in water, the strained liquor
            is called the decoction of the plant. --Arbuthnot.

            In pharmacy decoction is opposed to infusion, where
            there is merely steeping.             --Latham.

Source : WordNet®

decoction
     n : (pharmacology) the extraction by boiling of water-soluble
         drug substances