Source : Webster's Revised Unabridged Dictionary (1913)

Installment \In*stall"ment\, n. [Written also instalment.]
   1. The act of installing; installation.

            Take oaths from all kings and magistrates at their
            installment, to do impartial justice by law.
                                                  --Milton.

   2. The seat in which one is placed. [Obs.]

            The several chairs of order, look, you scour; . . .
            Each fair installment, coat, and several crest With
            loyal blazon, evermore be blest.      --Shak.

   3. A portion of a debt, or sum of money, which is divided
      into portions that are made payable at different times.
      Payment by installment is payment by parts at different
      times, the amounts and times being often definitely
      stipulated. --Bouvier.

Source : WordNet®

installment
     n 1: a payment of part of a debt; usually paid at regular
          intervals
     2: a part of a broadcast serial [syn: {episode}, {instalment}]
     3: a part of a published serial [syn: {instalment}]
     4: the act of installing something (as equipment); "the
        telephone installation took only a few minutes" [syn: {installation},
         {installing}, {instalment}]